Corects a bnuch of typeos throuhgout teh Fluter codebsae.

Made use of the `misspell` tool:
https://github.com/client9/misspell

* 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

* 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

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

* fix indentof statements in BlockFunctionBody

* fix indentof statements in BlockFunctionBody in tests

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* Don't send accept/reject if compilation never started.

Ensure that we wait for reject's response since that is async operation.

Fixes https://github.com/flutter/flutter/issues/27120.

* Fix analysis errors

* Rename flag. Ensure we raise it on first compilation too.

* Add support for experimental flags during hot reload.

* Revert "Make UriMapper and StdoutHandler public and add test cases (#26932)"

This reverts commit 6cf554b0.

* Revert "Update packages (#27046)"

This reverts commit 496c5738.

* Revert "roll engine for TODAY bug (#27049)"

This reverts commit 5ae6346f.

* Revert "Warn when building on master channel (#25007)"

This reverts commit dd65a546.

* Revert "Add experimentalBuildEnabled flag and initial shim for build_runner (#26989)"

This reverts commit 1237ee8f.

* Revert "Experimental flags for hot reloads, fixed (#27043)"

This reverts commit 2c05d08f.