This reverts commit e38be671.

https://github.com/flutter/engine/compare/d4d4883216fd...b68f7e72aa71

git log d4d4883216fd1c1dfc17d41418a960c002cfff57..b68f7e72aa71eb75969bd674d78a5b40ee5ed89f --no-merges --oneline
b68f7e72a Allow specifying an alternate Mac host SDK. (flutter/engine#8249)
3df694300 Roll src/third_party/dart cabaa78cc5..ba0147ac07 (3 commits) (flutter/engine#8248)
69c4d82f5 Roll src/third_party/skia d6ab77a2e20f..19fb3971bca5 (17 commits) (flutter/engine#8245)
06635d38a Mirror Android platform views a11y tree in the Flutter a11y tree. (flutter/engine#8237)
28433c513 FlutterJNI no longer asserts it is attached when dispatching platform messages and instead fizzles with a warning if not attached. Not sure what root cause of issue is, but this is necessary to avoid crashes. (flutter/engine#8246)
1addfb596 Roll src/third_party/dart 5e9df35a57..cabaa78cc5 (36 commits) (flutter/engine#8244)
13e3b7101 Roll src/third_party/skia a695da930510..d6ab77a2e20f (11 commits) (flutter/engine#8243)

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This results in running Flutter Gallery with one less thread (platform
and gpu threads are the the same).

This is very likely to cause a regression in the iOS Gallery benchmarks.
I'm mainly interested in landing this to see how much the benchmarks
regress, and it's likely that we will revert it shortly after landing.

* have tests that log error messages use a FakePlatform that does not support Ansi color, to fix tests started from color terminals
* add the override to the other tests too, in case someone copy & pastes them in the future for a test involving an error message

https://github.com/flutter/engine/compare/250b99bd275a...d4d4883216fd

git log 250b99bd275ad7622f239a8042f6a6d31b5b95f1..d4d4883216fd1c1dfc17d41418a960c002cfff57 --no-merges --oneline
d4d488321 Roll src/third_party/skia 174a3f61fd5d..a695da930510 (2 commits) (flutter/engine#8242)
2d5376c09 Roll src/third_party/skia 2c4ceca62d27..174a3f61fd5d (1 commits) (flutter/engine#8239)
b05399901 Roll src/third_party/skia e409441aee0d..2c4ceca62d27 (1 commits) (flutter/engine#8238)

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250b99bd2 Roll src/third_party/skia 4652930a7dfc..e409441aee0d (1 commits) (flutter/engine#8236) (#29719)


https://github.com/flutter/engine/compare/fa435385b6b9...250b99bd275a

git log fa435385b6b9f80080997dd38ad66bbe4bb0a152..250b99bd275ad7622f239a8042f6a6d31b5b95f1 --no-merges --oneline
250b99bd2 Roll src/third_party/skia 4652930a7dfc..e409441aee0d (1 commits) (flutter/engine#8236)

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* Use source list from the compiler to track invalidated files.

* Revert accidental change

* Fix first-time-seen-the-file logic

* Fix/simplify invalidate logic now that we can rely on compiler to let us know what is the cut-off point for invalidation.

* Update devfs mock to accommodate for new fields

* Fix deleted files case

* Analyzer found missing final

https://github.com/flutter/engine/compare/188adf7e5ec5...fa435385b6b9

git log 188adf7e5ec521f7859d5a0a1609fdcb688436b2..fa435385b6b9f80080997dd38ad66bbe4bb0a152 --no-merges --oneline
fa435385b Use the GPU thread for Android surface on-screen context lifecycle operations (flutter/engine#8234)
10e1addd8 Roll src/third_party/skia 7e2c0614a2fd..4652930a7dfc (5 commits) (flutter/engine#8232)

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https://github.com/flutter/engine/compare/d8c89e2bfe9b...188adf7e5ec5

git log d8c89e2bfe9b0b0d50da41c1349ef1534517c3c8..188adf7e5ec521f7859d5a0a1609fdcb688436b2 --no-merges --oneline
188adf7e5 Removed Activity reference from AccessibilityBridge by using a View for insets instead of the Activity (#18115) (flutter/engine#8231)
d452dd5c3 Initial import of GLFW Linux shell from FDE (flutter/engine#8159)
512004503 Remove jsoncpp from desktop Linux shell setup (flutter/engine#8230)

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* Composite physical layers even if elevation is 0

https://github.com/flutter/engine/compare/6a8a45fc4f69...d8c89e2bfe9b

git log 6a8a45fc4f698364d03b5902c1818d2acc79db22..d8c89e2bfe9b0b0d50da41c1349ef1534517c3c8 --no-merges --oneline
d8c89e2bf Add the Linux desktop setup script to Dockerfile (flutter/engine#8227)

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[Material] Create a FloatingActionButton ThemeData and honor it within the FloatingActionButton (#28735)

Adds a FloatingActionButtonThemeData so that FABs can be themed at the Theme level and independently. The properties that are now on the theme must be defaulted at the build level, in order to respect any contributing theme properties. Because of this, some tests had to be modified to look at properties after they are built. Also, since default behaviors are now tested in the FAB Theme test, some default tests in the FAB test no longer applied and were removed.

The themable properties are:
-backgroundColor
-foregroundColor
-elevation
-disabledElevation
-highlightElevation
-shape

https://github.com/flutter/engine/compare/96ad0c8926b0...6a8a45fc4f69

git log 96ad0c8926b0493d4276a39ee9bc6de6fa97bece..6a8a45fc4f698364d03b5902c1818d2acc79db22 --no-merges --oneline
6a8a45fc4 Have the AccessibilityBridge attach/detach itself to the (flutter/engine#8229)
45b19e47c Roll src/third_party/skia ba91f65f2070..7e2c0614a2fd (13 commits) (flutter/engine#8228)
1dbd2046b Moved io.flutter.embedding.engine.android package to io.flutter.embedding.android (flutter/engine#8221)
bb354363e Roll src/third_party/dart 70e3e67dd7..5e9df35a57 (45 commits)
3b19a4d30 Removed dart_plugin_tag from DEPS
d9b6629b6 Roll src/third_party/skia 4273a150f84d..ba91f65f2070 (6 commits) (flutter/engine#8225)
e88573aef Roll src/third_party/skia d7d93001ead2..4273a150f84d (1 commits) (flutter/engine#8224)
be9067cc7 Roll src/third_party/skia 37a9294d2eb9..d7d93001ead2 (2 commits) (flutter/engine#8223)
ee4abba58 Roll src/third_party/skia 2894d13a0d9b..37a9294d2eb9 (1 commits) (flutter/engine#8222)
3496156bd Roll src/third_party/skia dd0544078d05..2894d13a0d9b (33 commits) (flutter/engine#8220)
a1dcb2ea9 [ios] Set contentsScale before we commit CATransaction (flutter/engine#8218)
fa1931f6a Send macOS keyboard data to the engine (flutter/engine#8219)
45f69ac47 Plumb a reference of PlatformViewsController and AccessibilityBridge to each other (flutter/engine#8208)
7cbbdb400 libtxt: more accurate tracking of run positioning and width for justified text (flutter/engine#8214)
172810342 Add a build dependencies script for Linux desktop (flutter/engine#8160)
d764b69b2 Add docs for helpful commands to fix format (flutter/engine#8171)

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* some space formattings

* always use blocks in if-else if a block is used

* format spaces in for and while

* allow multiline if conditions

* fix missing space

Reverting to the engine version prior to:
https://github.com/flutter/flutter/pull/29658

3496156bd Roll src/third_party/skia dd0544078d05..2894d13a0d9b (33 commits) (flutter/engine#8220) (#29659)


https://github.com/flutter/engine/compare/a1dcb2ea987e...3496156bd9bf

git log a1dcb2ea987efe0e257832160a1b0583ac219584..3496156bd9bfe61788bf64ce3ca3cf1bc2663f95 --no-merges --oneline
3496156bd Roll src/third_party/skia dd0544078d05..2894d13a0d9b (33 commits) (flutter/engine#8220)

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https://github.com/flutter/engine/compare/96ad0c8926b0...a1dcb2ea987e

git log 96ad0c8926b0493d4276a39ee9bc6de6fa97bece..a1dcb2ea987efe0e257832160a1b0583ac219584 --no-merges --oneline
a1dcb2ea9 [ios] Set contentsScale before we commit CATransaction (flutter/engine#8218)
fa1931f6a Send macOS keyboard data to the engine (flutter/engine#8219)
45f69ac47 Plumb a reference of PlatformViewsController and AccessibilityBridge to each other (flutter/engine#8208)
7cbbdb400 libtxt: more accurate tracking of run positioning and width for justified text (flutter/engine#8214)
172810342 Add a build dependencies script for Linux desktop (flutter/engine#8160)
d764b69b2 Add docs for helpful commands to fix format (flutter/engine#8171)

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* Manual engine roll for 2019-03-19
* Applying patch for Dart SDK changes (see PR #29004)