Add unsized color-renderable formats to getInternalformatParameter

Per Kbr's suggestion in https://github.com/KhronosGroup/WebGL/pull/1362,
getInternalformatParameter should succeed for the unsized
color-renderable formats, and return an array containing the value 0 for
the SAMPLES parameter query.

BUG=295792
TEST=deqp/functional/gles3/internalformatquery.html

Review URL: https://codereview.chromium.org/1518803004

Cr-Commit-Position: refs/heads/master@{#364882}
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index 3b1d79c..48618af 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -327,6 +327,11 @@
     bool floatType = false;
 
     switch (internalformat) {
+    // Renderbuffer doesn't support unsized internal formats,
+    // though GL_RGB and GL_RGBA are color-renderable.
+    case GL_RGB:
+    case GL_RGBA:
+    // Multisampling is not supported for signed and unsigned integer internal formats.
     case GL_R8UI:
     case GL_R8I:
     case GL_R16UI: