WebGL 2: remove incorrect enum value for buffer in clearBuffer

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index 9bcdef10823c499b90510d95fd38bc47d8fa44b5..c76b1ed6530b8f5797f613ba2d6582b6c8655b2a 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -1605,9 +1605,6 @@ bool WebGL2RenderingContextBase::validateClearBuffer(const char* functionName, G
 {
     switch (buffer) {
     case GL_COLOR:
-    case GL_FRONT:
-    case GL_BACK:
-    case GL_FRONT_AND_BACK:

[qiankun, 2016/01/13 06:11:35]

INVALID_EUNUM should be genereated for the invalid buffer. See Page 190 in ES
3.0.4 spec: https://www.khronos.org/registry/gles/specs/3.0/es_spec_3.0.4.pdf.

I think you can add tests to validate this.

[yunchao, 2016/01/13 07:52:18]

It is not possible to expose the error by adding webgl conformance test for this
case, because the command buffer has validation code to verify the argument
'buffer'. Command buffer service side can report INVALID_ENUM against
FRONT/BACK/FRONT_AND_BACK.

However, validateClearBuffer() is necessary to verify the 'size' argument. We
can not remove this function. 

         if (size < 4) {
             synthesizeGLError(GL_INVALID_VALUE, functionName, "invalid array size");
             return false;