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..b45d921ddc996136d79f11dcb3636051fb8bd5bc 100644
--- a/cc/blink/web_external_texture_layer_impl.cc
+++ b/cc/blink/web_external_texture_layer_impl.cc
@@ -61,6 +61,24 @@ void WebExternalTextureLayerImpl::setNearestNeighbor(bool nearest_neighbor) {
       ->SetNearestNeighbor(nearest_neighbor);
 }
 
+static gfx::ColorSpace toGfxColorSpace(const SkColorSpace* skColorSpace) {

[danakj, 2016/08/12 21:03:48]

how about SkColorSpaceToColorSpace (like SkRectToRectF and friends)

also use chromium style please for function and variable names

[Justin Novosad, 2016/08/15 18:07:03]

Done.

+  // TODO(crbug.com/634102): eliminate this clumsy conversion by unifying
+  // SkColorSpace and gfx::ColorSpace

[danakj, 2016/08/12 21:03:48]

comments need punctuation and capitalization

[Justin Novosad, 2016/08/15 18:07:03]

Done.

+  if (!skColorSpace)
+    return gfx::ColorSpace();
+
+  // Assumption: using srgb or linear-rgb

[danakj, 2016/08/12 21:03:48]

comments need punctuation, should be proper sentences. but this is literally
saying what the DCHECK is doing, not explaining it. remove?

[Justin Novosad, 2016/08/15 18:07:03]

Done.

+  DCHECK(skColorSpace->gammaNamed() == SkColorSpace::kSRGB_GammaNamed ||
+         skColorSpace->gammaNamed() == SkColorSpace::kLinear_GammaNamed);
+  gfx::ColorSpace::TransferID transfer =
+      skColorSpace->gammaNamed() == SkColorSpace::kSRGB_GammaNamed

[danakj, 2016/08/12 21:03:48]

can this be a switch instead? so new enum values force people to update here? or
would that be bad?

[Justin Novosad, 2016/08/15 18:07:04]

Done.

+          ? gfx::ColorSpace::TransferID::IEC61966_2_1
+          : gfx::ColorSpace::TransferID::LINEAR;
+  return gfx::ColorSpace::ColorSpace(gfx::ColorSpace::PrimaryID::BT709,

[danakj, 2016/08/12 21:03:48]

what is gfx::ColorSpace::ColorSpace()? is that the constructor..? I didnt know
you can write it that way if so.

[Justin Novosad, 2016/08/15 18:07:04]

This was bad code. somehow the compiler was letting me get away with it on
linux.  Try bots failed on some other platforms.

+                                     transfer, gfx::ColorSpace::MatrixID::RGB,
+                                     gfx::ColorSpace::RangeID::FULL);
+}
+
 bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
     cc::TextureMailbox* mailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* release_callback,
@@ -97,6 +115,7 @@ 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(