adds WARP support to Chromium, for Metro mode only, on Windows 8

content/browser/gpu/gpu_data_manager_impl_private.cc

Index: content/browser/gpu/gpu_data_manager_impl_private.cc
diff --git a/content/browser/gpu/gpu_data_manager_impl_private.cc b/content/browser/gpu/gpu_data_manager_impl_private.cc
index fd705c8967ac20837a5d2c6b45f039d7c71b3fa2..2f362d6038015282ed8cfc32754e7ad4ce4c4291 100644
--- a/content/browser/gpu/gpu_data_manager_impl_private.cc
+++ b/content/browser/gpu/gpu_data_manager_impl_private.cc
@@ -271,7 +271,7 @@ bool GpuDataManagerImplPrivate::IsFeatureBlacklisted(int feature) const {
     return true;
   }
 #endif  // OS_CHROMEOS
-  if (use_swiftshader_) {
+  if (use_swiftshader_ || ShouldUseWarp()) {
     // Skia's software rendering is probably more efficient than going through
     // software emulation of the GPU, so use that.
     if (feature == gpu::GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS)
@@ -287,7 +287,7 @@ bool GpuDataManagerImplPrivate::IsDriverBugWorkaroundActive(int feature) const {
 }
 
 size_t GpuDataManagerImplPrivate::GetBlacklistedFeatureCount() const {
-  if (use_swiftshader_)
+  if (use_swiftshader_ || ShouldUseWarp())
     return 1;
   return blacklisted_features_.size();
 }
@@ -311,7 +311,7 @@ void GpuDataManagerImplPrivate::GetGpuProcessHandles(
 
 bool GpuDataManagerImplPrivate::GpuAccessAllowed(
     std::string* reason) const {
-  if (use_swiftshader_)
+  if (use_swiftshader_ || ShouldUseWarp())
     return true;
 
   if (!gpu_process_accessible_) {
@@ -398,6 +398,11 @@ void GpuDataManagerImplPrivate::RegisterSwiftShaderPath(
   EnableSwiftShaderIfNecessary();
 }
 
+bool GpuDataManagerImplPrivate::ShouldUseWarp() const {
+  return use_warp_ ||
+      CommandLine::ForCurrentProcess()->HasSwitch(switches::kUseWarp);
+}
+
 void GpuDataManagerImplPrivate::AddObserver(GpuDataManagerObserver* observer) {
   GpuDataManagerImpl::UnlockedSession session(owner_);
   observer_list_->AddObserver(observer);
@@ -545,7 +550,7 @@ void GpuDataManagerImplPrivate::UpdateGpuInfoHelper() {
 
 void GpuDataManagerImplPrivate::UpdateGpuInfo(const gpu::GPUInfo& gpu_info) {
   // No further update of gpu_info if falling back to SwiftShader.
-  if (use_swiftshader_)
+  if (use_swiftshader_ || ShouldUseWarp())
     return;
 
   gpu::MergeGPUInfo(&gpu_info_, gpu_info);
@@ -645,6 +650,9 @@ void GpuDataManagerImplPrivate::AppendGpuCommandLine(
       gpu_info_.driver_vendor);
   command_line->AppendSwitchASCII(switches::kGpuDriverVersion,
       gpu_info_.driver_version);
+
+  if (ShouldUseWarp())
+    command_line->AppendSwitch(switches::kUseWarp);
 }
 
 void GpuDataManagerImplPrivate::AppendPluginCommandLine(
@@ -707,6 +715,7 @@ void GpuDataManagerImplPrivate::DisableHardwareAcceleration() {
   for (int i = 0; i < gpu::NUMBER_OF_GPU_FEATURE_TYPES; ++i)
     blacklisted_features_.insert(i);
 
+  EnableWarpIfNecessary();
   EnableSwiftShaderIfNecessary();
   NotifyGpuInfoUpdate();
 }
@@ -813,6 +822,8 @@ bool GpuDataManagerImplPrivate::UpdateActiveGpu(
 }
 
 bool GpuDataManagerImplPrivate::CanUseGpuBrowserCompositor() const {
+  if (ShouldUseWarp())
+    return true;
   if (ShouldUseSwiftShader())
     return false;
   if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_GPU_COMPOSITING))
@@ -859,6 +870,7 @@ GpuDataManagerImplPrivate::GpuDataManagerImplPrivate(
     : complete_gpu_info_already_requested_(false),
       observer_list_(new GpuDataManagerObserverList),
       use_swiftshader_(false),
+      use_warp_(false),
       card_blacklisted_(false),
       update_histograms_(true),
       window_count_(0),
@@ -932,6 +944,7 @@ void GpuDataManagerImplPrivate::UpdateBlacklistedFeatures(
     blacklisted_features_.insert(gpu::GPU_FEATURE_TYPE_WEBGL);
   }
 
+  EnableWarpIfNecessary();
   EnableSwiftShaderIfNecessary();
 }
 
@@ -957,6 +970,9 @@ void GpuDataManagerImplPrivate::NotifyGpuInfoUpdate() {
 }
 
 void GpuDataManagerImplPrivate::EnableSwiftShaderIfNecessary() {
+  if (ShouldUseWarp())
+    return;
+
   if (!GpuAccessAllowed(NULL) ||
       blacklisted_features_.count(gpu::GPU_FEATURE_TYPE_WEBGL)) {
     if (!swiftshader_path_.empty() &&
@@ -966,6 +982,22 @@ void GpuDataManagerImplPrivate::EnableSwiftShaderIfNecessary() {
   }
 }
 
+void GpuDataManagerImplPrivate::EnableWarpIfNecessary() {
+#if defined(OS_WIN)
+  if (use_warp_)
+    return;
+  // We should only use WARP if we are unable to use the regular GPU for
+  // compositing, and if we in Metro mode.
+  use_warp_ =
+      CommandLine::ForCurrentProcess()->HasSwitch(switches::kViewerConnect) &&
+      !CanUseGpuBrowserCompositor();
+#endif
+}
+
+void GpuDataManagerImplPrivate::ForceWarpModeForTesting() {
+  use_warp_ = true;
+}
+
 std::string GpuDataManagerImplPrivate::GetDomainFromURL(
     const GURL& url) const {
   // For the moment, we just use the host, or its IP address, as the