Support dynamic switching between integrated and discrete GPUs on Mac OS X.

Change Chrome to allocate most OpenGL contexts with the
kCGLPFAAllowOfflineRenderers flag, and specify
NSSupportsAutomaticGraphicsSwitching in the Info.plist for the main
executable and helper apps. This keeps Chrome on the integrated GPU
except when using WebGL, accelerated 2D Canvas, Pepper 3D, and Core
Animation-based plugins (except Flash).

Chrome shares resources between OpenGL contexts in order to display WebGL
and other content in the compositor, and resource sharing doesn't work
between contexts allocated on different GPUs. Therefore, when the first
context for a given renderer requests the discrete GPU, the channel is
dropped and all contexts are reallocated on the discrete GPU. Similarly,
when the last context requesting the discrete GPU for a given renderer is
shut down, all contexts are dropped and reallocated on the integrated GPU.

Currently dynamic GPU switching is only supported on the latest Mac OS X
10.7 update and MacBook Pros with dual AMD / Intel GPUs, though this will
improve in future OS updates.

Tested with WebGL, CSS 3D, Flash and Unity3D content and observed desired
GPU switching behavior. Also added a layout test to WebKit under
https://bugs.webkit.org/show_bug.cgi?id=69776 which when run in Chrome
catches an assertion failure related to the destruction of contexts. The
intent is to add it as a UI layout test on the GPU bots.

BUG=88788
TEST=none
Review URL: http://codereview.chromium.org/8233027

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@105399 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 36 insertions, 12 deletions

diff --git a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
index 6e14dad..ec03290 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
+++ b/webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc
@@ -103,7 +103,8 @@ class GLInProcessContext : public base::SupportsWeakPtr<GLInProcessContext> {
       GLInProcessContext* context_group,
       const char* allowed_extensions,
       const int32* attrib_list,
-      const GURL& active_arl);
+      const GURL& active_url,
+      gfx::GpuPreference gpu_preference);
 
   // Create a GLInProcessContext that renders to an offscreen frame buffer. If
   // parent is not NULL, that GLInProcessContext can access a copy of the
@@ -119,7 +120,8 @@ class GLInProcessContext : public base::SupportsWeakPtr<GLInProcessContext> {
       GLInProcessContext* context_group,
       const char* allowed_extensions,
       const int32* attrib_list,
-      const GURL& active_url);
+      const GURL& active_url,
+      gfx::GpuPreference gpu_preference);
 
   // For an offscreen frame buffer GLInProcessContext, return the texture ID
   // with respect to the parent GLInProcessContext. Returns zero if
@@ -173,7 +175,8 @@ class GLInProcessContext : public base::SupportsWeakPtr<GLInProcessContext> {
                   GLInProcessContext* context_group,
                   const char* allowed_extensions,
                   const int32* attrib_list,
-                  const GURL& active_url);
+                  const GURL& active_url,
+                  gfx::GpuPreference gpu_preference);
   void Destroy();
 
   void OnSwapBuffers();
@@ -240,7 +243,8 @@ GLInProcessContext* GLInProcessContext::CreateViewContext(
     GLInProcessContext* context_group,
     const char* allowed_extensions,
     const int32* attrib_list,
-    const GURL& active_url) {
+    const GURL& active_url,
+    gfx::GpuPreference gpu_preference) {
 #if defined(ENABLE_GPU)
   scoped_ptr<GLInProcessContext> context(new GLInProcessContext(NULL));
   if (!context->Initialize(
@@ -250,7 +254,8 @@ GLInProcessContext* GLInProcessContext::CreateViewContext(
       context_group,
       allowed_extensions,
       attrib_list,
-      active_url))
+      active_url,
+      gpu_preference))
     return NULL;
 
   return context.release();
@@ -265,7 +270,8 @@ GLInProcessContext* GLInProcessContext::CreateOffscreenContext(
     GLInProcessContext* context_group,
     const char* allowed_extensions,
     const int32* attrib_list,
-    const GURL& active_url) {
+    const GURL& active_url,
+    gfx::GpuPreference gpu_preference) {
 #if defined(ENABLE_GPU)
   scoped_ptr<GLInProcessContext> context(new GLInProcessContext(parent));
   if (!context->Initialize(
@@ -275,7 +281,8 @@ GLInProcessContext* GLInProcessContext::CreateOffscreenContext(
       context_group,
       allowed_extensions,
       attrib_list,
-      active_url))
+      active_url,
+      gpu_preference))
     return NULL;
 
   return context.release();
@@ -397,7 +404,8 @@ bool GLInProcessContext::Initialize(bool onscreen,
                                     GLInProcessContext* context_group,
                                     const char* allowed_extensions,
                                     const int32* attrib_list,
-                                    const GURL& active_url) {
+                                    const GURL& active_url,
+                                    gfx::GpuPreference gpu_preference) {
   // Use one share group for all contexts.
   static scoped_refptr<gfx::GLShareGroup> share_group(new gfx::GLShareGroup);
 
@@ -480,7 +488,9 @@ bool GLInProcessContext::Initialize(bool onscreen,
     return false;
   }
 
-  context_ = gfx::GLContext::CreateGLContext(share_group.get(), surface_.get());
+  context_ = gfx::GLContext::CreateGLContext(share_group.get(),
+                                             surface_.get(),
+                                             gpu_preference);
   if (!context_.get()) {
     LOG(ERROR) << "Could not create GLContext.";
     Destroy();
@@ -625,6 +635,13 @@ bool WebGraphicsContext3DInProcessCommandBufferImpl::initialize(
 
   const char* preferred_extensions = "*";
 
+  // TODO(kbr): More work will be needed in this implementation to
+  // properly support GPU switching. Like in the out-of-process
+  // command buffer implementation, all previously created contexts
+  // will need to be lost either when the first context requesting the
+  // discrete GPU is created, or the last one is destroyed.
+  gfx::GpuPreference gpu_preference = gfx::PreferDiscreteGpu;
+
   GURL active_url;
   if (web_view && web_view->mainFrame())
     active_url = GURL(web_view->mainFrame()->document().url());
@@ -653,7 +670,8 @@ bool WebGraphicsContext3DInProcessCommandBufferImpl::initialize(
       context_group ? context_group->context_ : NULL,
       preferred_extensions,
       attribs,
-      active_url);
+      active_url,
+      gpu_preference);
   web_view_ = NULL;
 
   if (!context_)
diff --git a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
index 4506289..c56e222 100644
--- a/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
+++ b/webkit/gpu/webgraphicscontext3d_in_process_impl.cc
@@ -164,8 +164,13 @@ bool WebGraphicsContext3DInProcessImpl::initialize(
       return false;
   }
 
+  // TODO(kbr): This implementation doesn't yet support lost contexts
+  // and therefore can't yet properly support GPU switching.
+  gfx::GpuPreference gpu_preference = gfx::PreferDiscreteGpu;
+
   gl_context_ = gfx::GLContext::CreateGLContext(share_group,
-                                                gl_surface_.get());
+                                                gl_surface_.get(),
+                                                gpu_preference);
   if (!gl_context_.get()) {
     if (!is_gles2_)
       return false;
@@ -180,7 +185,8 @@ bool WebGraphicsContext3DInProcessImpl::initialize(
     if (webView) webView->mainFrame()->collectGarbage();
 
     gl_context_ = gfx::GLContext::CreateGLContext(share_group,
-                                                  gl_surface_.get());
+                                                  gl_surface_.get(),
+                                                  gpu_preference);
     if (!gl_context_.get())
       return false;
   }