Add compositor support for half-float RGBA buffers and textures

cc/resources/resource_format_utils.cc

Index: cc/resources/resource_format_utils.cc
diff --git a/cc/resources/resource_format_utils.cc b/cc/resources/resource_format_utils.cc
index 788f687adfbe81e13d55a96dc4bcefdc10f33682..8118160dcb9da65f72d344d8c66df813983a265d 100644
--- a/cc/resources/resource_format_utils.cc
+++ b/cc/resources/resource_format_utils.cc
@@ -24,6 +24,8 @@ SkColorType ResourceFormatToClosestSkColorType(ResourceFormat format) {
     case RED_8:
     case LUMINANCE_F16:
       return kN32_SkColorType;
+    case RGBA_F16:
+      return kRGBA_F16_SkColorType;
   }
   NOTREACHED();
   return kN32_SkColorType;