Fix MaterialApp's _navigatorObserver so it doesn't cause WidgetApp's assertion to fail when using custom navigator, fixes #18904

https://github.com/flutter/engine/compare/0f70d5d4f1e3...219bf5938752

git log 0f70d5d4f1e3ed377781bc6e73e3666c73afc7f8..219bf5938752e0030b491565af1910c137b83dd8 --no-merges --oneline
219bf5938 Roll src/third_party/skia 1383a38e1d92..e4628b10722f (12 commits) (flutter/engine#8443)
a40adfdf4 Add window title/icon support to GLFW shell (flutter/engine#8435)

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https://github.com/flutter/engine/compare/5944867cabdb...0f70d5d4f1e3

git log 5944867cabdb934ef9fea0dccb865cb1acef51b5..0f70d5d4f1e3ed377781bc6e73e3666c73afc7f8 --no-merges --oneline
0f70d5d4f Roll src/third_party/dart 600b2831ef..9814cb1b9c (7 commits)
4b1ec56bc Roll src/third_party/skia f346df396a23..1383a38e1d92 (8 commits) (flutter/engine#8440)

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Adds the "2D Transformations" demo to the gallery, which shows how to do things such as navigate around a map a la Google Maps, or show a full screen zoomable photo.  The idea is to abstract this code into a first class widget soon.

* Fix: ui.PointerChange.remove might contain position change, but we used to expand it into a Cancel and Remove, neither of which allows position change. A Hover event is added, and a test is updated accordingly.
* Fixed the issue where a PointerMoveEvent and a PointerCancelEvent do not receive the correct pressure.
* Refactor the calculation of delta into deltaTo.

https://github.com/flutter/engine/compare/ad9d2417e9aa...5944867cabdb

git log ad9d2417e9aa182700f0d1423de758d2a000598d..5944867cabdb934ef9fea0dccb865cb1acef51b5 --no-merges --oneline
5944867ca update to use SkTileMode (flutter/engine#8439)

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https://github.com/flutter/engine/compare/309d078b597d...ad9d2417e9aa

git log 309d078b597d3a38fe9bcef8d8bae7b56487e8eb..ad9d2417e9aa182700f0d1423de758d2a000598d --no-merges --oneline
ad9d2417e Roll src/third_party/skia dde12a25bb5e..f346df396a23 (1 commits) (flutter/engine#8438)
0ed237c19 Roll src/third_party/skia b6d04556c34d..dde12a25bb5e (4 commits) (flutter/engine#8437)
445ab42ef Roll src/third_party/dart 11a3dd7332..600b2831ef (9 commits)
49d0dc6d6 Roll src/third_party/skia 5c5de2146309..b6d04556c34d (1 commits) (flutter/engine#8434)
4ff18fbda Roll src/third_party/dart f6768b6fb3..11a3dd7332 (56 commits)
7b831986f Roll src/third_party/skia 2273c900ea28..5c5de2146309 (5 commits) (flutter/engine#8432)
800ea0a40 Revert "Enable shutting down all root isolates in a VM. (#8402)" (flutter/engine#8431)
b59c4436c Enable shutting down all root isolates in a VM. (flutter/engine#8402)
9acdf1837 Make AccessibilityViewEmbedder final (flutter/engine#8429)
804d54ddf Eliminate unused displayBounds parameter (flutter/engine#8427)
d4c815f57 Roll buildroot (flutter/engine#8425)
20190d707 Roll src/third_party/skia fbe240669394..2273c900ea28 (13 commits) (flutter/engine#8428)
7e38b0aa2 Revert "Revert "Separate the data required to bootstrap the VM into its own class. (#8397)" (#8406)" (flutter/engine#8414)
d8bb9d793 Roll src/third_party/skia 176da0bb8a10..fbe240669394 (9 commits) (flutter/engine#8424)
64fc58329 Remove use of DART_CHECK_VALID. (flutter/engine#8417)

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309d078b5 Roll src/third_party/skia e25b4472cdd9..176da0bb8a10 (10 commits) (flutter/engine#8422) (#30441)


https://github.com/flutter/engine/compare/cc115500b9cb...309d078b597d

git log cc115500b9cb2b27d59627f202e6cd6bb87f49fc..309d078b597d3a38fe9bcef8d8bae7b56487e8eb --no-merges --oneline
309d078b5 Roll src/third_party/skia e25b4472cdd9..176da0bb8a10 (10 commits) (flutter/engine#8422)

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This reverts commit ffbb335e.

Reason for revert: flutter driver tests may have bugs in getting
first frame. Revert this until we figure out what happened.

This flag makes flutter build aot report timings for substeps (e.g.
frontend compilation and gen_snapshot) in a machine readable form.

https://github.com/flutter/engine/compare/4a8c7dceeb4b...cc115500b9cb

git log 4a8c7dceeb4b7c710e0b22090cc3bc26f458a3a9..cc115500b9cb2b27d59627f202e6cd6bb87f49fc --no-merges --oneline
cc115500b Roll src/third_party/skia c9eeab3d85b9..e25b4472cdd9 (1 commits) (flutter/engine#8420)
20e45996d Roll src/third_party/skia 71c0e9422038..c9eeab3d85b9 (4 commits) (flutter/engine#8418)
a650790e4 Add scroll wheel support to desktop GLFW shell (flutter/engine#8416)
77d8e12e9 Roll src/third_party/dart 14fd3b7d6a..f6768b6fb3 (5 commits)
23fceaacd Added new Android embedding packages to javadoc generation. (flutter/engine#8411)
2f1786010 Pass environment defines to compile flutter platform step. (flutter/engine#8412)

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Cupertino localization step 4: let generated date localization combine material and cupertino locales (#29650)

* Draggable Scrollable sheet

https://github.com/flutter/engine/compare/f7b4903d7c99...4a8c7dceeb4b

git log f7b4903d7c9913447af3aaebc4308d1a1e2a4dde..4a8c7dceeb4b7c710e0b22090cc3bc26f458a3a9 --no-merges --oneline
4a8c7dcee Roll src/third_party/skia f2d9b865d736..71c0e9422038 (13 commits) (flutter/engine#8413)
efbecd7e8 [txt] Add back FontCollection::SetDefaultFontManager (flutter/engine#8410)
5f7711449 Roll src/third_party/dart 75b2f9f919..14fd3b7d6a (23 commits)
f27c5730a [fuchsia] Exclude glfw from the Fuchsia host build (flutter/engine#8407)
853ac1bdf Roll src/third_party/skia 70d8f4f3acbb..f2d9b865d736 (11 commits) (flutter/engine#8408)

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There were 2 possible scenarios in which _handleAppFrame is added more than once as a frame callback. When this happens it is possible that the second invocation will try to access _nextFrame.image when _nextFrame is null and crash. The 2 scenarios are:

Scenario 1

A GIF frame is decoded and a Flutter frame is executed before it's time to show the next GIF frame.
The timer that's waiting for enough time to elapse is invoked, and schedules a callback for the next Flutter frame(here).
Before the next Flutter frame is executed, MultiFrameImageStreamCompleter#removeListener is called followed by ``MultiFrameImageStreamCompleter#addListenerthat is invoking_decodeNextFrameAndSchedule` which is adding `_handleAppFrame` again as a next frame callback.
Scenario 2
removeListener and addListener are called multiple times in succession, every call to addListener can result in another registration of _handleAppFrame to the next Flutter frame callbacks list.

This patch fixes the issue by guarding against a second registration of _handleAppFrame.

https://github.com/flutter/engine/compare/6675f71dfb22...f7b4903d7c99

git log 6675f71dfb22a0b4fdab6332e37843f78c33c9e6..f7b4903d7c9913447af3aaebc4308d1a1e2a4dde --no-merges --oneline
f7b4903d7 Revert "Separate the data required to bootstrap the VM into its own class. (#8397)" (flutter/engine#8406)
f835789dd Roll src/third_party/skia d962070feb84..70d8f4f3acbb (1 commits) (flutter/engine#8405)

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6675f71df Roll src/third_party/skia 1acf79a3e5b8..d962070feb84 (4 commits) (flutter/engine#8404) (#30365)


https://github.com/flutter/engine/compare/b572ade3550b...6675f71dfb22

git log b572ade3550b3f04ccb8c18d5bc4d5804f479c03..6675f71dfb22a0b4fdab6332e37843f78c33c9e6 --no-merges --oneline
6675f71df Roll src/third_party/skia 1acf79a3e5b8..d962070feb84 (4 commits) (flutter/engine#8404)

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b572ade35 Roll src/third_party/skia 3f6a2ac63670..1acf79a3e5b8 (1 commits) (flutter/engine#8403) (#30355)


https://github.com/flutter/engine/compare/3796d989183d...b572ade3550b

git log 3796d989183d588b17a110d8aaf74906c4e1c8f0..b572ade3550b3f04ccb8c18d5bc4d5804f479c03 --no-merges --oneline
b572ade35 Roll src/third_party/skia 3f6a2ac63670..1acf79a3e5b8 (1 commits) (flutter/engine#8403)

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https://github.com/flutter/engine/compare/79a988f5da46...3796d989183d

git log 79a988f5da4665980c6cc6916403e76b53f1e3e0..3796d989183d588b17a110d8aaf74906c4e1c8f0 --no-merges --oneline
3796d9891 [ui] Add null check in FontWeight.lerp (flutter/engine#8274)

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https://github.com/flutter/engine/compare/c991647404f8...79a988f5da46

git log c991647404f8117dab2ca4ed49aa3ba48a634240..79a988f5da4665980c6cc6916403e76b53f1e3e0 --no-merges --oneline
79a988f5d Roll src/third_party/skia b27667a15a15..3f6a2ac63670 (1 commits) (flutter/engine#8401)
cfe8675ff Delay platform view removal to submitFrame. (flutter/engine#8380)

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https://github.com/flutter/engine/compare/6c1b0b83c2b3...c991647404f8

git log 6c1b0b83c2b3259cf7b23c2f6d6fc5cfdb924b61..c991647404f8117dab2ca4ed49aa3ba48a634240 --no-merges --oneline
c99164740 Separate the data required to bootstrap the VM into its own class. (flutter/engine#8397)
8c9aca440 Roll src/third_party/skia de206c75c2c8..b27667a15a15 (14 commits) (flutter/engine#8399)

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