Correct typos, adopt US spellings (flutter#9081)

Corects a bnuch of typeos throughout teh engien codebsae. Also makes
a couple minor Commonwealth -> US spelling adjustments for consistency
with the rest of Flutter's codebase.

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

Author: cbracken

ci/licenses.sh

@@ -36,7 +36,7 @@ then
     echo "changed, no diffs are typically expected in the output of the"
     echo "script. Verify the output, and if it looks correct, update the"
     echo "license tool signature golden file:"
-    echo "  ci/licences_golden/tool_signature"
+    echo "  ci/licenses_golden/tool_signature"
     echo "For more information, see the script in:"
     echo "  https://github.com/flutter/engine/tree/master/tools/licenses"
     echo ""

ci/licenses_golden/tool_signature

@@ -1,2 +1,2 @@
-Signature: ab4f82ed4f38f0d3821073855c220992
+Signature: ad6590b867473860a1e6b08bf9e98667
 

fml/platform/linux/timerfd.cc

@@ -46,7 +46,7 @@ bool TimerRearm(int fd, fml::TimePoint time_point) {
 }
 
 bool TimerDrain(int fd) {
-  // 8 bytes must be read from a signalled timer file descriptor when signalled.
+  // 8 bytes must be read from a signaled timer file descriptor when signaled.
   uint64_t fire_count = 0;
   ssize_t size = FML_HANDLE_EINTR(::read(fd, &fire_count, sizeof(uint64_t)));
   if (size != sizeof(uint64_t)) {

fml/platform/linux/timerfd.h

@@ -46,7 +46,7 @@ namespace fml {
 /// Rearms the timer to expire at the given time point.
 bool TimerRearm(int fd, fml::TimePoint time_point);
 
-/// Drains the timer FD and retuns true if it has expired. This may be false in
+/// Drains the timer FD and returns true if it has expired. This may be false in
 /// case the timer read is non-blocking and this routine was called before the
 /// timer expiry.
 bool TimerDrain(int fd);

lib/stub_ui/lib/src/engine/dom_renderer.dart

@@ -51,7 +51,7 @@ class DomRenderer {
   html.Element get sceneElement => _sceneElement;
   html.Element _sceneElement;
 
-  /// This is state persistant across hot restarts that indicates what
+  /// This is state persistent across hot restarts that indicates what
   /// to clear.  We delay removal of old visible state to make the
   /// transition appear smooth.
   static const String _staleHotRestartStore = '__flutter_state';

lib/stub_ui/lib/src/engine/semantics/semantics.dart

@@ -1067,7 +1067,7 @@ class EngineSemanticsOwner {
 
   /// Declares that the [child] must be attached to the [parent].
   ///
-  /// Attachments take precendence over detachments (see [_detachObject]). This
+  /// Attachments take precedence over detachments (see [_detachObject]). This
   /// allows the same node to be detached from one parent in the tree and
   /// reattached to another parent.
   void _attachObject({SemanticsObject parent, SemanticsObject child}) {

lib/stub_ui/lib/src/ui/painting.dart

@@ -1600,7 +1600,7 @@ enum FilterQuality {
 
   /// Fastest possible filtering, albeit also the lowest quality.
   ///
-  /// Typically this implies nearest-neighbour filtering.
+  /// Typically this implies nearest-neighbor filtering.
   none,
 
   /// Better quality than [none], faster than [medium].
@@ -1804,7 +1804,7 @@ Future<void> _decodeImageFromListAsync(
 /// [pixels] is the pixel data in the encoding described by [format].
 ///
 /// [rowBytes] is the number of bytes consumed by each row of pixels in the
-/// data buffer.  If unspecified, it defaults to [width] multipled by the
+/// data buffer.  If unspecified, it defaults to [width] multiplied by the
 /// number of bytes per pixel in the provided [format].
 void decodeImageFromPixels(Uint8List pixels, int width, int height,
     PixelFormat format, ImageDecoderCallback callback,
@@ -1883,7 +1883,7 @@ class Shadow {
   ///
   /// This class does not provide a way to disable shadows to avoid inconsistencies
   /// in shadow blur rendering, primarily as a method of reducing test flakiness.
-  /// [toPaint] should be overriden in subclasses to provide this functionality.
+  /// [toPaint] should be overridden in subclasses to provide this functionality.
   Paint toPaint() {
     return Paint()
       ..color = color

lib/stub_ui/lib/src/ui/semantics.dart

@@ -175,7 +175,7 @@ class SemanticsAction {
   /// A [Snackbar], for example, may have a dismiss action to indicate to the
   /// user that it can be removed after it is no longer relevant. On Android,
   /// (with TalkBack) special hint text is spoken when focusing the node and
-  /// a custom action is availible in the local context menu. On iOS,
+  /// a custom action is available in the local context menu. On iOS,
   /// (with VoiceOver) users can perform a standard gesture to dismiss it.
   static const SemanticsAction dismiss =
       const SemanticsAction._(_kDismissIndex);
@@ -431,7 +431,7 @@ class SemanticsFlag {
   /// that the node's semantic label can be used to announce an edge triggered
   /// semantics update.
   ///
-  /// Semantic nodes annotated with this flag will still recieve a11y focus.
+  /// Semantic nodes annotated with this flag will still receive a11y focus.
   ///
   /// Updating this label within the same active route subtree will not cause
   /// additional announcements.

lib/stub_ui/lib/src/ui/text.dart

@@ -423,7 +423,7 @@ class TextStyle {
   /// * `fontWeight`: The typeface thickness to use when painting the text (e.g., bold).
   /// * `fontStyle`: The typeface variant to use when drawing the letters (e.g., italics).
   /// * `fontFamily`: The name of the font to use when painting the text (e.g., Roboto). If a `fontFamilyFallback` is
-  ///   provided and `fontFamily` is not, then the first font family in `fontFamilyFallback` will take the postion of
+  ///   provided and `fontFamily` is not, then the first font family in `fontFamilyFallback` will take the position of
   ///   the preferred font family. When a higher priority font cannot be found or does not contain a glyph, a lower
   ///   priority font will be used.
   /// * `fontFamilyFallback`: An ordered list of the names of the fonts to fallback on when a glyph cannot

lib/stub_ui/lib/src/ui/window.dart

@@ -944,7 +944,7 @@ class Window {
 
   /// Change the retained semantics data about this window.
   ///
-  /// If [semanticsEnabled] is true, the user has requested that this funciton
+  /// If [semanticsEnabled] is true, the user has requested that this function
   /// be called whenever the semantic content of this window changes.
   ///
   /// In either case, this function disposes the given update, which means the