Implement on demand quad rasterization for PicturePiles.

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index ad27935e03ccabc9e832a23307984086f88205a0..6ab35a36881a98e37c738e47d297129135b2b2a8 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2641,7 +2641,8 @@ TEST_F(LayerTreeHostImplTest, layersFreeTextures)
 
     m_hostImpl->active_tree()->SetRootLayer(rootLayer.Pass());
 
-    EXPECT_EQ(0u, context3d->NumTextures());
+    // An auxiliary texture is created for on-demand rasterization.
+    EXPECT_EQ(1u, context3d->NumTextures());
 
     LayerTreeHostImpl::FrameData frame;
     EXPECT_TRUE(m_hostImpl->PrepareToDraw(&frame));
@@ -2649,12 +2650,12 @@ TEST_F(LayerTreeHostImplTest, layersFreeTextures)
     m_hostImpl->DidDrawAllLayers(frame);
     m_hostImpl->SwapBuffers();
 
-    EXPECT_GT(context3d->NumTextures(), 0u);
+    EXPECT_GT(context3d->NumTextures(), 1u);
 
     // Kill the layer tree.
     m_hostImpl->active_tree()->SetRootLayer(LayerImpl::Create(m_hostImpl->active_tree(), 100));
     // There should be no textures left in use after.
-    EXPECT_EQ(0u, context3d->NumTextures());
+    EXPECT_EQ(1u, context3d->NumTextures());
 }
 
 class MockDrawQuadsToFillScreenContext : public TestWebGraphicsContext3D {