Add color metadata info to VideoDecoderConfig.

ui/gfx/color_space.h

Index: ui/gfx/color_space.h
diff --git a/ui/gfx/color_space.h b/ui/gfx/color_space.h
index b7b93786a55309b9e54596ab68498093c01a4d19..4f417ded7f5ea7798bceac09e03b370bdc6718cb 100644
--- a/ui/gfx/color_space.h
+++ b/ui/gfx/color_space.h
@@ -70,6 +70,7 @@ class GFX_EXPORT ColorSpace {
     BT2020_12 = 15,
     SMPTEST2084 = 16,
     SMPTEST428_1 = 17,
+    ARIB_STD_B67 = 18,  // AKA hybrid-log gamma, HLG

[hubbe, 2016/09/15 17:25:52]

Also need to add this to ToLinear/FromLinear in color_transform.cc and
associated unit tests.

[servolk, 2016/09/15 20:29:04]

Done.
I've found some conversion formulas in Wikipedia
(https://en.wikipedia.org/wiki/Hybrid_Log-Gamma) and at
https://github.com/videovillage/Lattice-Issues/issues/52. Adding Steven to check
these are correct. IIUC we should use the formulas for the values normalized to
0..1 range here, right?
I think I might have done something wrong, since ColorSpaceTests start failing
when I add ARIB_STD_B67 into the all_transfers in color_transform_unittest.cc

PS: I've extracted the changes to add the new ARIB/HLG transfer function in a
separate CL so that it's easier to review and address gfx_unittest failures in
isolation from the rest of this CL:
https://codereview.chromium.org/2342963003/

[hubbe, 2016/09/15 20:46:12]

+1 for moving to a separate CL.
The 0-1 normalization is not clear. The specs that I followed for the other
transfer functions doesn't do that in all cases.

 
     // Chrome-specific values start at 1000.
     GAMMA24 = 1000,
@@ -108,10 +109,14 @@ class GFX_EXPORT ColorSpace {
   // We use an enum instead of a bool becuase different bit depths may have
   // different definitions of what "limited" means.
   enum class RangeID : int8_t {
-    FULL = 0,
+    UNSPECIFIED = 0,
     LIMITED = 1,
+    FULL = 2,
 
-    LAST = LIMITED
+    // Defined by TransferID/MatrixID
+    DERIVED = 3,
+
+    LAST = DERIVED
   };
 
   ColorSpace();