Renaming unit_test class MockCanvas to not collide.

PageOverlayTest and PrintContextTest both use a local mock
test class named MockCanvas for testing. That is normally
no big deal but in jumbo builds they can be compiled
in the same translation unit and then the classes
will collide. This patch gives the classes unique names.

R=fs@opera.com

Change-Id: Icfcb2b4b553e50e08cb6ac56712e4e9aa5f2b69e
Reviewed-on: https://chromium-review.googlesource.com/574349Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#487065}

third_party/WebKit/Source/core/page/PageOverlayTest.cpp

@@ -109,9 +109,9 @@ class RuntimeFeatureChange {
   bool old_value_;
 };
 
-class MockCanvas : public SkCanvas {
+class MockPageOverlayCanvas : public SkCanvas {
  public:
-  MockCanvas(int width, int height) : SkCanvas(width, height) {}
+  MockPageOverlayCanvas(int width, int height) : SkCanvas(width, height) {}
   MOCK_METHOD2(onDrawRect, void(const SkRect&, const SkPaint&));
 };
 
@@ -128,7 +128,7 @@ TEST_F(PageOverlayTest, PageOverlay_AcceleratedCompositing) {
   // page overlay actually winds up getting drawn on top of the rest.
   // For now, we just check that the GraphicsLayer will draw the right thing.
 
-  MockCanvas canvas(kViewportWidth, kViewportHeight);
+  MockPageOverlayCanvas canvas(kViewportWidth, kViewportHeight);
   EXPECT_CALL(canvas, onDrawRect(_, _)).Times(AtLeast(0));
   EXPECT_CALL(canvas,
               onDrawRect(SkRect::MakeWH(kViewportWidth, kViewportHeight),