Adds a test that verifies that the microtask queue is flushed between
engine event loop iterations.

Related issue: https://github.com/flutter/flutter/issues/9998

I got tired of drive-by spelling fixes, so I figured I'd just take care of them all at once.

This only corrects errors in the dartdocs, not regular comments, and I skipped any sample code in the dartdocs. It doesn't touch any identifiers in the dartdocs either. No code changes, just comments.

This fixes DropdownButtons to align their popups correctly in RTL as well.

Also while I was there I fixed the issue with text scale factor in the gallery.

Previously, we were mapping certain named platforms
(e.g. `android-stable`) to their corresponding version.
this had two problems:

1. The version could become out of date. For instance, we had
   mapped `android-stable` to version 24, but the stable version
   is now 27.
2. The list of possible named versions wasn't comprehensive.
   Some Android SDKs just list the platform as `stable`, or
   `experimental`, etc.

This change updates the platform version detection to use
the `build.prop` file that exists in the platform directory
(only for cases where the version number is not encoded into
the directory name).

This is the first engine role with libwebp, so we expect an increase in
flutter app sizes.
I'll be monitoring the app size benchmarks after this lands.

Previously, ExpansionPanel would do weird things if interacted with
when it was already animating. This is fixed and there's now a test.

Also:

 * Minor fixes to make the gallery work in RTL, not that there's
   any way to see that without hard-coding the framework to RTL.
   But at least I'll be less annoyed when doing that.

 * Some trivial code and documentation cleanup.

* custom hashCode/== in Element to speed up inheritFromWidgetOfExactType

* explain why 24 bits

This makes ListTile expand vertically when text is scaled, or really when whatever is placed inside it is larger than the available space.

In order for UnconstrainedBox to be useful here, I needed for it to only unconstrain the child Row in one dimension, so I added a "constrainedAxis" parameter to the UnconstrainedBox.

Also, changed one enum test to use a switch instead.

I modified the ListTile test to be more representative of the intention of the spec: we were testing with text in the leading and trailing sections, and the design wants icons there. Because there was leading text, and the dense mode only changes the font size on the text lines, the leading text was propping up the minimum size of the tile, making so that the test wasn't really testing any changes in dense mode.

* add git version comparison function

* use [] in dartdoc

* Make method instance method

* PageView ballistics overshoot the page on some devices

On some devices, such as Cupertino “Plus”-sized devices, scrolling left on the first page of a PageView will overshoot the first page and land on the second page.

The issue is that applyContentDimensions incorrectly detects a content size change due to a floating point comparison on certain screen sizes (18257.400000000005 vs 18257.4)

To fix this, perform a nearEqual comparison in applyContentDimensions.

* Apply style changes to nearEqual for code review feedback.

* Add text field content to semantics

* remove controller dup

Creates a new (hidden) flutter command 'ide-config' that will create and/or update
existing .iml files and some files under the .idea directory, as well as
removing existing *.iml files and the .idea directory.

It also:

 * Adds *.iml to the .gitignore
 * Removes existing .iml files from the repo, and moves them to the
   packages/flutter_tools/ide_templates/intellij directory.
 * Adds a flag to ide-config ('--update-templates') that will take any new .iml
   files in the flutter tree and add them to the existing templates.
     - If --overwrite is also specified, then all existing templates will also
       be overwritten with the contents from the flutter tree, and any that have
       been deleted from the flutter tree will also be removed from the
       templates.
 * Added new run configurations for all existing app targets that will now also
   be automatically added to IntelliJ.
 * Setting up the environment also includes setting the coding style guidelines
   and the git VCS.
 * Note that after this PR lands, Flutter developers will need to run it once to
   re-create the .iml files and configuration files that have been removed.

After this PR lands, .iml files will no longer appear in the untracked files
section for git.

If we fail to bind to IPv4 loopback, try IPv6. Some hosts only support IPv6,
causing the test in vmservice_test.dart to fail, since it couldn't find an
available port.

* Get rid of static version methods which ignore the AppContext

* Review comments

* Review Comments

* Make branch behave the same as original implementation

* Fix tests

* Implement MultiFrameImageStreamCompleter

* only decode frames while there are active listeners

* review comments followup

* multiply animation frame timer duration by time dilation

* lint

* tweak the text for the 'elements didnt reload' message

* review comments

* prefix items with a list char

* add a hostIsIde param instead of the isDaemonMode top-level function

* add a trailing comma

* Use IKG for restarts, use IKG with ProtectedFileByteStore.

* Fix comment, add end of file newline.

* Remove unused import