Make gfx::Rect class operations consistently mutate the class they are called on.

cc/draw_quad.cc

Index: cc/draw_quad.cc
diff --git a/cc/draw_quad.cc b/cc/draw_quad.cc
index 0967ce651ebe360fff8e7f5495cdca2b07773a64..ba6f8c0756ecb2c1a1a664db4429dc0b3dff9a45 100644
--- a/cc/draw_quad.cc
+++ b/cc/draw_quad.cc
@@ -43,7 +43,8 @@ gfx::Rect DrawQuad::opaqueRect() const
 
 void DrawQuad::setQuadVisibleRect(gfx::Rect quadVisibleRect)
 {
-    m_quadVisibleRect = quadVisibleRect.Intersect(m_quadRect);
+    m_quadVisibleRect = quadVisibleRect;
+    m_quadVisibleRect.Intersect(m_quadRect);
 }
 
 unsigned DrawQuad::size() const