ui: Replace std::vector with a simple array in ClipTransformRecorder.

ui/compositor/clip_transform_recorder.h

Index: ui/compositor/clip_transform_recorder.h
diff --git a/ui/compositor/clip_transform_recorder.h b/ui/compositor/clip_transform_recorder.h
index 84f340d75ac318475c173b5f2581f329b30578bf..276b845cf5b3351dd8036b7e0085b848a624fa5e 100644
--- a/ui/compositor/clip_transform_recorder.h
+++ b/ui/compositor/clip_transform_recorder.h
@@ -46,7 +46,10 @@ class COMPOSITOR_EXPORT ClipTransformRecorder {
     TRANSFORM,
   };
   const PaintContext& context_;
-  std::vector<Closer> closers_;
+  // If someone needs to do more than this many operations with a single
+  // ClipTransformRecorder then increase the size of the closers_ array.
+  Closer closers_[4];
+  size_t num_closers_;
 
   DISALLOW_COPY_AND_ASSIGN(ClipTransformRecorder);
 };