* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

* Use RenderAnimatedOpacity within AnimatedOpacity widget (#15466)

* Fixed minor bug in RenderAnimatedOpacity

* Updated protected API for ImplicitlyAnimatedWidget

This adds a toImage function to RenderRepaintBoundary that returns an uncompressed raw image of the RenderRepaintBoundary and its children. A device pixel ratio different from the physical ratio may be specified for the captured image. A value of 1.0 will give an image in logical pixels.

For backward compatibility we keep supporting specifying the shape as a
combination of MaterialType and borderRadius, and we just use that as a
default when shapeBorder is null.

To cleanup the implementation if shapeBorder was not specified we just
translate the specified shape to a shapeBorder internally.
I benchmarked paint, layout and hit testing, with the specialized shape
clippers vs. the equivalent path clippers and did not see any
significant performance difference.

For testing, I extended the clippers/physicalShape matchers to match either the
specialized shape or the equivalent shape.

This CL also refactors common logic for RenderPhysicalModel and
RenderPhysicalShape into a base class _RenderPhysicalModelBase.

* Oct 12 10:12am

* implicit_semantics_test.dart passes

* refactoring

* works in nice

* minor rename

* more doc comments

* to be explicit check better

* fix test

* ++

* ++

* semantics_9_test (BlockSemantics) and implicit_semantics_test are passing

* doc updates

* tiny refactor

* fix static errors in tests

* fix gesture detector

* ++

* ++

* geometry

* ++

* remove noGeometry

* revert test

* +

* all tests but scrolling/clipping pass

* clipping works

* scrolling halfway

* sliver tests pass

* ALL TESTS PASS

* SemanticsNode changed

* docs and tiny fixes

* card test

* more doc comments

* remove missed print

* more tests

* make test pass on Linux

* remove changes to intellij proj file

* review comments

* refactor to ensureAction + some related doc fixes

* Update docs for markNeedsSemanticsUpdate

* rewording

* rewording

* ensureAction test

* ensureAction test

* ensureAction test

* more tests

* refactor to allways reset node

* tiny fixes

* more test

* doc fixes

* one more test

* review comments

On Fuchsia, the system compositor is responsible for drawing shadows
for physical model layers with non-zero elevation.

Also fixed a bug where _needsCompositing was not being cleared prior
to updating it.

If the size is empty, then _updatePaintData will produce an invalid transform
that yields a NaN canvas bounds rectangle

Fixes https://github.com/flutter/flutter/issues/7431