Suppress some no-op GraphicsContext calls

Source/platform/graphics/GraphicsContext.cpp

Index: Source/platform/graphics/GraphicsContext.cpp
diff --git a/Source/platform/graphics/GraphicsContext.cpp b/Source/platform/graphics/GraphicsContext.cpp
index b51203fb649a04edd422aeaa76bd7d161e30f250..79f38d3483513d577e82d33e7016c8fe4d665bb7 100644
--- a/Source/platform/graphics/GraphicsContext.cpp
+++ b/Source/platform/graphics/GraphicsContext.cpp
@@ -465,6 +465,9 @@ bool GraphicsContext::concat(const SkMatrix& matrix)
     if (paintingDisabled())
         return false;
 
+    if (matrix.isIdentity())
+        return true;
+
     realizeSave(SkCanvas::kMatrix_SaveFlag);
 
     return m_canvas->concat(matrix);
@@ -562,7 +565,7 @@ void GraphicsContext::drawDisplayList(DisplayList* displayList)
 {
     ASSERT(!displayList->picture()->getRecordingCanvas());
 
-    if (paintingDisabled() || !displayList)
+    if (paintingDisabled() || !displayList || displayList->bounds().isEmpty())
         return;
 
     realizeSave(SkCanvas::kMatrixClip_SaveFlag);
@@ -1587,6 +1590,9 @@ void GraphicsContext::translate(float w, float h)
     if (paintingDisabled())
         return;
 
+    if (!w && !h)
+        return;
+
     realizeSave(SkCanvas::kMatrix_SaveFlag);
 
     m_canvas->translate(WebCoreFloatToSkScalar(w), WebCoreFloatToSkScalar(h));
@@ -1597,6 +1603,9 @@ void GraphicsContext::scale(const FloatSize& size)
     if (paintingDisabled())
         return;
 
+    if (size.width() == 1 && size.height() == 1)

[Stephen Chennney, 2014/01/17 21:53:21]

Not sure if the compiler automatically casts the 1 to 1.0f, but I feel more
comfortable with explicitly saying 1.0f.

+        return;
+
     realizeSave(SkCanvas::kMatrix_SaveFlag);
 
     m_canvas->scale(WebCoreFloatToSkScalar(size.width()), WebCoreFloatToSkScalar(size.height()));