Allow using a larger-than-necessary texture as cached render pass backing

cc/direct_renderer.cc

 // Copyright 2012 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/direct_renderer.h"
 
 #include <vector>
 
 #include "base/debug/trace_event.h"
 #include "base/metrics/histogram.h"
@@ skipping 95 matching lines @@
 DirectRenderer::DirectRenderer(RendererClient* client, ResourceProvider* resourceProvider)
     : Renderer(client)
     , m_resourceProvider(resourceProvider)
 {
 }
 
 DirectRenderer::~DirectRenderer()
 {
 }
 
+void DirectRenderer::setEnlargePassTextureAmountForTesting(gfx::Vector2d amount)
+{
+    m_enlargePassTextureAmount = amount;
+}
+
 void DirectRenderer::decideRenderPassAllocationsForFrame(const RenderPassList& renderPassesInDrawOrder)
 {
     base::hash_map<RenderPass::Id, const RenderPass*> renderPassesInFrame;
     for (size_t i = 0; i < renderPassesInDrawOrder.size(); ++i)
         renderPassesInFrame.insert(std::pair<RenderPass::Id, const RenderPass*>(renderPassesInDrawOrder[i]->id, renderPassesInDrawOrder[i]));
 
     std::vector<RenderPass::Id> passesToDelete;
     ScopedPtrHashMap<RenderPass::Id, CachedResource>::const_iterator passIterator;
     for (passIterator = m_renderPassTextures.begin(); passIterator != m_renderPassTextures.end(); ++passIterator) {
         base::hash_map<RenderPass::Id, const RenderPass*>::const_iterator it = renderPassesInFrame.find(passIterator->first);
         if (it == renderPassesInFrame.end()) {
             passesToDelete.push_back(passIterator->first);
             continue;
         }
 
         const RenderPass* renderPassInFrame = it->second;
         const gfx::Size& requiredSize = renderPassTextureSize(renderPassInFrame);
         GLenum requiredFormat = renderPassTextureFormat(renderPassInFrame);
         CachedResource* texture = passIterator->second;
         DCHECK(texture);
 
-        if (texture->id() && (texture->size() != requiredSize || texture->format() != requiredFormat))
+        bool sizeAppropriate = texture->size().width() >= requiredSize.width() &&
+                               texture->size().height() >= requiredSize.height();
+        if (texture->id() && (!sizeAppropriate || texture->format() != requiredFormat))
             texture->Free();
     }
 
     // Delete RenderPass textures from the previous frame that will not be used again.
     for (size_t i = 0; i < passesToDelete.size(); ++i)
         m_renderPassTextures.erase(passesToDelete[i]);
 
     for (size_t i = 0; i < renderPassesInDrawOrder.size(); ++i) {
         if (!m_renderPassTextures.contains(renderPassesInDrawOrder[i]->id)) {
           scoped_ptr<CachedResource> texture = CachedResource::create(m_resourceProvider);
@@ skipping 112 matching lines @@
 
     if (renderPass == frame.rootRenderPass) {
         bindFramebufferToOutputSurface(frame);
         initializeMatrices(frame, renderPass->output_rect, flippedFramebuffer());
         setDrawViewportSize(renderPass->output_rect.size());
         return true;
     }
 
     CachedResource* texture = m_renderPassTextures.get(renderPass->id);
     DCHECK(texture);
-    if (!texture->id() && !texture->Allocate(Renderer::ImplPool, renderPassTextureSize(renderPass), renderPassTextureFormat(renderPass), ResourceProvider::TextureUsageFramebuffer))
+
+    gfx::Size size = renderPassTextureSize(renderPass);
+    size.Enlarge(m_enlargePassTextureAmount.x(), m_enlargePassTextureAmount.y());
+    if (!texture->id() && !texture->Allocate(Renderer::ImplPool, size, renderPassTextureFormat(renderPass), ResourceProvider::TextureUsageFramebuffer))
         return false;
 
     return bindFramebufferToTexture(frame, texture, renderPass->output_rect);
 }
 
 bool DirectRenderer::haveCachedResourcesForRenderPassId(RenderPass::Id id) const
 {
     CachedResource* texture = m_renderPassTextures.get(id);
     return texture && texture->id() && texture->isComplete();
 }
 
 // static
 gfx::Size DirectRenderer::renderPassTextureSize(const RenderPass* pass)
 {
     return pass->output_rect.size();
 }
 
 // static
 GLenum DirectRenderer::renderPassTextureFormat(const RenderPass*)
 {
     return GL_RGBA;
 }
 
 }  // namespace cc