content: Add command line flag for native GPU memory buffers.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index ffe2ddb731aad2a0efd5550b35f3a2bde2d45b4c..42054c5bcfd02677d404e33eedbae0f52103659b 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -151,22 +151,6 @@ size_t GetMaxTransferBufferUsageBytes(
                   max_transfer_buffer_usage_bytes);
 }
 
-unsigned GetMapImageTextureTarget(
-    const ContextProvider::Capabilities& context_capabilities) {
-// TODO(reveman): This should be a setting passed to the compositor instead
-// of hard-coded here. The target that need to be used depends on our choice
-// of GpuMemoryBuffer type. Note: SURFACE_TEXTURE needs EXTERNAL_OES,
-// IO_SURFACE needs RECTANGLE_ARB. crbug.com/431059
-#if defined(OS_ANDROID)
-  if (context_capabilities.gpu.egl_image_external)
-    return GL_TEXTURE_EXTERNAL_OES;
-#endif
-  if (context_capabilities.gpu.texture_rectangle)
-    return GL_TEXTURE_RECTANGLE_ARB;
-
-  return GL_TEXTURE_2D;
-}
-
 size_t GetMaxStagingResourceCount() {
   // Upper bound for number of staging resource to allow.
   return 32;
@@ -1964,6 +1948,17 @@ void LayerTreeHostImpl::CreateResourceAndRasterWorkerPool(
   bool should_use_zero_copy_rasterizer =
       settings_.use_zero_copy || IsSynchronousSingleThreaded();
 
+  unsigned image_target = GL_TEXTURE_2D;
+#if defined(OS_MACOSX)
+  // GL_TEXTURE_RECTANGLE_ARB target is required by IOSurface backed images.
+  DCHECK(context_provider->ContextCapabilities().gpu.texture_rectangle);
+  image_target = GL_TEXTURE_RECTANGLE_ARB;
+#endif
+  if (settings_.use_image_external) {
+    DCHECK(context_provider->ContextCapabilities().gpu.egl_image_external);
+    image_target = GL_TEXTURE_EXTERNAL_OES;
+  }
+
   if (!context_provider) {
     *resource_pool =
         ResourcePool::Create(resource_provider_.get(),
@@ -1986,10 +1981,9 @@ void LayerTreeHostImpl::CreateResourceAndRasterWorkerPool(
                                     resource_provider_.get(),
                                     settings_.use_distance_field_text);
   } else if (should_use_zero_copy_rasterizer && CanUseZeroCopyRasterizer()) {
-    *resource_pool = ResourcePool::Create(
-        resource_provider_.get(),
-        GetMapImageTextureTarget(context_provider->ContextCapabilities()),
-        resource_provider_->best_texture_format());
+    *resource_pool =
+        ResourcePool::Create(resource_provider_.get(), image_target,
+                             resource_provider_->best_texture_format());
 
     TaskGraphRunner* task_graph_runner;
     if (IsSynchronousSingleThreaded()) {
@@ -2004,10 +1998,9 @@ void LayerTreeHostImpl::CreateResourceAndRasterWorkerPool(
         task_runner, task_graph_runner, resource_provider_.get());
   } else if (settings_.use_one_copy && CanUseOneCopyRasterizer()) {
     // We need to create a staging resource pool when using copy rasterizer.
-    *staging_resource_pool = ResourcePool::Create(
-        resource_provider_.get(),
-        GetMapImageTextureTarget(context_provider->ContextCapabilities()),
-        resource_provider_->best_texture_format());
+    *staging_resource_pool =
+        ResourcePool::Create(resource_provider_.get(), image_target,
+                             resource_provider_->best_texture_format());
     *resource_pool =
         ResourcePool::Create(resource_provider_.get(),
                              GL_TEXTURE_2D,