explicitly validating assumptions about positive matrix scale

cc/texture_layer_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/texture_layer_impl.h"
 
 #include "base/stringprintf.h"
 #include "cc/quad_sink.h"
 #include "cc/renderer.h"
 #include "cc/texture_draw_quad.h"
@@ skipping 27 matching lines @@
     if (!m_externalTextureResource)
         return;
 
     SharedQuadState* sharedQuadState = quadSink.useSharedQuadState(createSharedQuadState());
     appendDebugBorderQuad(quadSink, sharedQuadState, appendQuadsData);
 
     gfx::Rect quadRect(gfx::Point(), contentBounds());
     gfx::Rect opaqueRect(contentsOpaque() ? quadRect : gfx::Rect());
     scoped_ptr<TextureDrawQuad> quad = TextureDrawQuad::Create();
     quad->SetNew(sharedQuadState, quadRect, opaqueRect, m_externalTextureResource, m_premultipliedAlpha, m_uvRect, m_flipped);
-    quadSink.append(quad.PassAs<DrawQuad>(), appendQuadsData);
+
+    // Perform explicit clipping on a quad to avoid setting a scissor later.
+    if (sharedQuadState->is_clipped && quad->PerformClipping())
+        sharedQuadState->is_clipped = false;
+    if (!quad->rect.IsEmpty())
+        quadSink.append(quad.PassAs<DrawQuad>(), appendQuadsData);
 }
 
 void TextureLayerImpl::didDraw(ResourceProvider* resourceProvider)
 {
     if (!m_externalTextureResource)
         return;
     // FIXME: the following assert will not be true when sending resources to a
     // parent compositor. A synchronization scheme (double-buffering or
     // pipelining of updates) for the client will need to exist to solve this.
     DCHECK(!resourceProvider->inUseByConsumer(m_externalTextureResource));
@@ skipping 13 matching lines @@
     m_textureId = 0;
     m_externalTextureResource = 0;
 }
 
 const char* TextureLayerImpl::layerTypeAsString() const
 {
     return "TextureLayer";
 }
 
 }  // namespace cc