use preferDiscreteGpu attribute in WebGraphicsContext3D initialization

content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc

Index: content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
diff --git a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
index ea5f90d78151db78e0026a1ef679b03d66b1bf18..c2f6d60147251dcc50cd168502dba6e5e8a2d6e7 100644
--- a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
+++ b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
@@ -92,10 +92,7 @@ bool WebGraphicsContext3DCommandBufferImpl::Initialize(
   if (!factory)
     return false;
 
-  // The noExtensions and canRecoverFromContextLoss flags are
-  // currently used as hints that we are creating a context on
-  // behalf of WebGL or accelerated 2D canvas, respectively.
-  if (attributes.noExtensions || !attributes.canRecoverFromContextLoss)
+  if (attributes.preferDiscreteGPU)
     gpu_preference_ = gfx::PreferDiscreteGpu;
 
   bool retry = false;