* MouseRegion documentation claimed that onEnter and onExit
  would track entry and exit regardless of whether the pointer was
  down or up
* It did such, but when grabbing the value of `event.down` from
  the passed event, the value was always `false`
* PointerEnterEvent and PointerExitEvent were overriding the value
  passed from PointerEvent in constructors, even if the value was true
  e.g. in invocations of .fromMouseEvent((PointerMoveEvent...))
* This change now passes the value along to PointerEnter/ExitEvents
  while providing it a default of false, and updates documentation

Fixes #40637

This fixes the mouse hover code to not schedule frames with every mouse move.

Before this, it would schedule a post frame callback, and then schedule a frame immediately, even if there was nothing that needed to be updated. Now it will schedule checks for mouse position updates synchronously, unless there's a new annotation, and skip scheduling a new frame in all cases. It has to be async in the case of a new annotation (i.e. a new MouseRegion is added), since when the annotation is added, it hasn't yet painted, and it can't hit test against the new layer until after the paint, so in that case it schedules a post frame callback, but since it's already building a frame when it does that, it doesn't need to schedule a frame.

The code also used to do mouse position checks for all mice if only one mouse changed position. I fixed this part too, so that it will only check position for the mouse that changed.

git@github.com:flutter/engine.git/compare/223d6d3e4278...b520d7fd4b6d

git log 223d6d3e4278..b520d7fd4b6d --no-merges --oneline
2019-09-26 bkonyi@google.com Roll src/third_party/dart 53564db036..6ff8d2199d (1 commits)


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This reverts commit 652be88e.

This fix is in https://github.com/flutter/packages/pull/37

git@github.com:flutter/engine.git/compare/1060cfc7daae...223d6d3e4278

git log 1060cfc7daae..223d6d3e4278 --no-merges --oneline
2019-09-26 bkonyi@google.com Roll src/third_party/dart dd65f97118..53564db036 (6 commits)


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git@github.com:flutter/engine.git/compare/9fd35df9bb47...1060cfc7daae

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2019-09-26 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/mac-amd64 from KcXAg... to z3PaM... (flutter/engine#12458)


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git@github.com:flutter/engine.git/compare/3713ecf10728...9fd35df9bb47

git log 3713ecf10728..9fd35df9bb47 --no-merges --oneline
2019-09-26 bkonyi@google.com Roll src/third_party/dart c6a14f4459..dd65f97118 (3 commits)


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git@github.com:flutter/engine.git/compare/b3f2aad1c64d...3713ecf10728

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2019-09-26 bkonyi@google.com Roll src/third_party/dart 6c81690c3a..c6a14f4459 (13 commits)


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git@github.com:flutter/engine.git/compare/3360d861e5cf...b3f2aad1c64d

git log 3360d861e5cf..b3f2aad1c64d --no-merges --oneline
2019-09-26 gspencergoog@users.noreply.github.com Revert "Send TYPE_VIEW_FOCUSED for views with input focus. (#12410)" (flutter/engine#12455)
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from worpw... to PyQPO... (flutter/engine#12452)
2019-09-25 bkonyi@google.com Roll src/third_party/dart 69b5681546..6c81690c3a (38 commits)
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/mac-amd64 from avi05... to KcXAg... (flutter/engine#12449)
2019-09-25 gspencergoog@users.noreply.github.com Send TYPE_VIEW_FOCUSED for views with input focus. (flutter/engine#12410)


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* Revert "Roll engine c1773f3c57eb..739ee77864e3 (3 commits) (#41331)"

This reverts commit 5caad71f.

* Revert "c1773f3c5 Send TYPE_VIEW_FOCUSED for views with input focus. (flutter/engine#12410) (#41325)"

This reverts commit ab8cf947.

git@github.com:flutter/engine.git/compare/c1773f3c57eb...739ee77864e3

git log c1773f3c57eb..739ee77864e3 --no-merges --oneline
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from worpw... to PyQPO... (flutter/engine#12452)
2019-09-25 bkonyi@google.com Roll src/third_party/dart 69b5681546..6c81690c3a (38 commits)
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/mac-amd64 from avi05... to KcXAg... (flutter/engine#12449)


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git@github.com:flutter/engine.git/compare/3360d861e5cf...c1773f3c57eb

git log 3360d861e5cf..c1773f3c57eb --no-merges --oneline
2019-09-25 gspencergoog@users.noreply.github.com Send TYPE_VIEW_FOCUSED for views with input focus. (flutter/engine#12410)


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git@github.com:flutter/engine.git/compare/efb7bf434f2c...3360d861e5cf

git log efb7bf434f2c..3360d861e5cf --no-merges --oneline
2019-09-25 yjbanov@google.com [web] filter test targets; cache host.dart compilation (flutter/engine#12445)


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* Update image_list test to use locally set up https server to validate performance of image loading over https(rather than http) protocol. Https requires more back-and-forward communication before image bytes are sent to the client, shows clear signs of throughput affected by how busy flutter UI isolate is.

This enables the manual tests to be built on a macOS desktop machine in desktop mode.

I created the macos directory by using flutter create --macos

git@github.com:flutter/engine.git/compare/0bfca375b3f5...efb7bf434f2c

git log 0bfca375b3f5..efb7bf434f2c --no-merges --oneline
2019-09-25 mklim@google.com Work around Samsung keyboard issue (flutter/engine#12432)


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Fixing the editable_text unit tests by clearing the log. Add a modification for also testing cached size. (#41300)

git@github.com:flutter/engine.git/compare/48ad8a08e45f...0bfca375b3f5

git log 48ad8a08e45f..0bfca375b3f5 --no-merges --oneline
2019-09-25 yjbanov@google.com Force exit felt tool on sigint, sigterm (flutter/engine#12443)
2019-09-25 skia-flutter-autoroll@skia.org Roll src/third_party/skia 6abaff3041a3..559ffe4a23ce (2 commits) (flutter/engine#12444)
2019-09-25 dworsham@google.com [fuchsia] Wire up OpacityLayer to Scenic (flutter/engine#11322)
2019-09-25 yjbanov@google.com delete golden files; switch to flutter/goldens (flutter/engine#12434)


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git@github.com:flutter/engine.git/compare/63949eb0fd98...48ad8a08e45f

git log 63949eb0fd98..48ad8a08e45f --no-merges --oneline
2019-09-25 devoncarew@google.com add dart:html, dart:js, and dart:js_util to the copy of the Dart SDK used for analysis (flutter/engine#12435)
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from dmzjj... to worpw... (flutter/engine#12441)
2019-09-25 skia-flutter-autoroll@skia.org Roll src/third_party/skia 2da97da4b024..6abaff3041a3 (1 commits) (flutter/engine#12440)
2019-09-25 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/mac-amd64 from rEYHD... to avi05... (flutter/engine#12439)
2019-09-25 skia-flutter-autoroll@skia.org Roll src/third_party/skia 2137f90b9d98..2da97da4b024 (3 commits) (flutter/engine#12438)
2019-09-25 skia-flutter-autoroll@skia.org Roll src/third_party/skia f050422f3285..2137f90b9d98 (4 commits) (flutter/engine#12437)
2019-09-25 ditman@gmail.com Interpret negative radii as 0 in recording_canvas drawDRRect (flutter/engine#12431)


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Manual roll of the engine to 63949eb0fd982b27adc218364805913380af7411.