Add some plumbing for the color management of canvases

cc/blink/web_external_texture_layer_impl.cc

Index: cc/blink/web_external_texture_layer_impl.cc
diff --git a/cc/blink/web_external_texture_layer_impl.cc b/cc/blink/web_external_texture_layer_impl.cc
index 2eef8658361ce36e26bad09113ed390b5d4ac225..08c37106c45ce81c2da23f3082ccc651ef090b3b 100644
--- a/cc/blink/web_external_texture_layer_impl.cc
+++ b/cc/blink/web_external_texture_layer_impl.cc
@@ -61,6 +61,22 @@ void WebExternalTextureLayerImpl::setNearestNeighbor(bool nearest_neighbor) {
       ->SetNearestNeighbor(nearest_neighbor);
 }
 
+static gfx::ColorSpace toGfxColorSpace(const SkColorSpace* skColorSpace) {
+  // TODO(crbug.com/634102): eliminate this clumsy conversion by unifying
+  // SkColorSpace and gfx::ColorSpace
+  if (!skColorSpace)
+    return gfx::ColorSpace::ColorSpace();
+
+  // assumption: using srgb or linear-rgb

[Stephen White, 2016/08/11 20:41:27]

Assert that assumption?

[Justin Novosad, 2016/08/12 17:40:18]

Done.

+  gfx::ColorSpace::TransferID transfer =
+      skColorSpace->gammaNamed() == SkColorSpace::kSRGB_GammaNamed
+          ? gfx::ColorSpace::TransferID::IEC61966_2_1
+          : gfx::ColorSpace::TransferID::LINEAR;
+  return gfx::ColorSpace::ColorSpace(gfx::ColorSpace::PrimaryID::BT709,
+                                     transfer, gfx::ColorSpace::MatrixID::RGB,
+                                     gfx::ColorSpace::RangeID::FULL);
+}
+
 bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
     cc::TextureMailbox* mailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* release_callback,
@@ -97,6 +113,7 @@ bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
         client_mailbox.allowOverlay, false);
   }
   mailbox->set_nearest_neighbor(client_mailbox.nearestNeighbor);
+  mailbox->set_color_space(toGfxColorSpace(client_mailbox.colorSpace));
 
   if (mailbox->IsValid()) {
     *release_callback = cc::SingleReleaseCallback::Create(