Remove trailing white spaces (#5708)

So our future pull requests won't be polluted by the white space changes.

lib/ui/compositing.dart

@@ -145,14 +145,14 @@ class SceneBuilder extends NativeFieldWrapperClass2 {
   ///
   /// Rasterization will be clipped to the given shape defined by [path]. If
   /// [elevation] is greater than 0.0, then a shadow is drawn around the layer.
-  /// [shadowColor] defines the color of the shadow if present and [color] defines the 
+  /// [shadowColor] defines the color of the shadow if present and [color] defines the
   /// color of the layer background.
   ///
   /// See [pop] for details about the operation stack.
   void pushPhysicalShape({ Path path, double elevation, Color color, Color shadowColor}) {
     _pushPhysicalShape(path, elevation, color.value, shadowColor?.value ?? 0xFF000000);
   }
-  void _pushPhysicalShape(Path path, double elevation, int color, int shadowColor) native 
+  void _pushPhysicalShape(Path path, double elevation, int color, int shadowColor) native
     'SceneBuilder_pushPhysicalShape';
 
   /// Ends the effect of the most recently pushed operation.

lib/ui/painting/path.h

@@ -85,14 +85,14 @@ class CanvasPath : public fxl::RefCountedThreadSafe<CanvasPath>,
   void addPolygon(const tonic::Float32List& points, bool close);
   void addRRect(const RRect& rrect);
   void addPath(CanvasPath* path, double dx, double dy);
-  void addPathWithMatrix(CanvasPath* path, 
-                         double dx, 
-                         double dy, 
+  void addPathWithMatrix(CanvasPath* path,
+                         double dx,
+                         double dy,
                          tonic::Float64List& matrix4);
   void extendWithPath(CanvasPath* path, double dx, double dy);
-  void extendWithPathAndMatrix(CanvasPath* path, 
-                               double dx, 
-                               double dy, 
+  void extendWithPathAndMatrix(CanvasPath* path,
+                               double dx,
+                               double dy,
                                tonic::Float64List& matrix4);
   void close();
   void reset();

lib/ui/semantics.dart

@@ -441,7 +441,7 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
   /// length and contain the same ids. They may only differ in the order the
   /// ids are listed in. For more information about different child orders, see
   /// [DebugSemanticsDumpOrder].
-  /// 
+  ///
   /// The system retains the nodes that are currently reachable from the root.
   /// A given update need not contain information for nodes that do not change
   /// in the update. If a node is not reachable from the root after an update,

lib/ui/text.dart

@@ -359,7 +359,7 @@ class TextStyle {
     Locale locale,
     Paint background,
     Paint foreground,
-  }) : assert(color == null || foreground == null, 
+  }) : assert(color == null || foreground == null,
          'Cannot provide both a color and a foreground\n'
          'The color argument is just a shorthand for "foreground: new Paint()..color = color".'
        ),