Add compositor support for half-float RGBA buffers and textures

cc/resources/resource_format.cc

Index: cc/resources/resource_format.cc
diff --git a/cc/resources/resource_format.cc b/cc/resources/resource_format.cc
index 2d139ab5c0465e910b289844893c6acb63a3653f..a7db8a780823461b560942dee98a6f581eda4041 100644
--- a/cc/resources/resource_format.cc
+++ b/cc/resources/resource_format.cc
@@ -12,6 +12,8 @@ namespace cc {
 
 int BitsPerPixel(ResourceFormat format) {
   switch (format) {
+    case RGBA_F16:
+      return 64;
     case BGRA_8888:
     case RGBA_8888:
       return 32;
@@ -42,6 +44,7 @@ GLenum GLDataType(ResourceFormat format) {
       GL_UNSIGNED_BYTE,           // ETC1
       GL_UNSIGNED_BYTE,           // RED_8
       GL_HALF_FLOAT_OES,          // LUMINANCE_F16
+      GL_HALF_FLOAT_OES,          // RGBA_F16
   };
   static_assert(arraysize(format_gl_data_type) == (RESOURCE_FORMAT_MAX + 1),
                 "format_gl_data_type does not handle all cases.");
@@ -61,6 +64,7 @@ GLenum GLDataFormat(ResourceFormat format) {
       GL_ETC1_RGB8_OES,  // ETC1
       GL_RED_EXT,        // RED_8
       GL_LUMINANCE,      // LUMINANCE_F16
+      GL_RGBA,           // RGBA_F16
   };
   static_assert(arraysize(format_gl_data_format) == (RESOURCE_FORMAT_MAX + 1),
                 "format_gl_data_format does not handle all cases.");
@@ -91,6 +95,7 @@ GLenum GLCopyTextureInternalFormat(ResourceFormat format) {
       GL_RGB,        // ETC1
       GL_LUMINANCE,  // RED_8
       GL_LUMINANCE,  // LUMINANCE_F16
+      GL_RGBA,       // RGBA_F16
   };
   static_assert(arraysize(format_gl_data_format) == (RESOURCE_FORMAT_MAX + 1),
                 "format_gl_data_format does not handle all cases.");
@@ -113,6 +118,7 @@ gfx::BufferFormat BufferFormat(ResourceFormat format) {
     case LUMINANCE_8:
     case RGB_565:
     case LUMINANCE_F16:
+    case RGBA_F16:
       break;
   }
   NOTREACHED();
@@ -129,6 +135,7 @@ bool DoesResourceFormatSupportAlpha(ResourceFormat format) {
     case RGBA_8888:
     case BGRA_8888:
     case ALPHA_8:
+    case RGBA_F16:
       return true;
     case LUMINANCE_8:
     case RGB_565: