Determine WebGL back-buffer on Mali-400 GPU

Source/core/html/canvas/WebGLRenderingContextBase.cpp

Index: Source/core/html/canvas/WebGLRenderingContextBase.cpp
diff --git a/Source/core/html/canvas/WebGLRenderingContextBase.cpp b/Source/core/html/canvas/WebGLRenderingContextBase.cpp
index 81550c6b5c79f743e923a2ce6fb6608fa4b07017..35b79306c6fd03a6aed39e60ebc93e3324e65a06 100644
--- a/Source/core/html/canvas/WebGLRenderingContextBase.cpp
+++ b/Source/core/html/canvas/WebGLRenderingContextBase.cpp
@@ -1455,6 +1455,9 @@ void WebGLRenderingContextBase::colorMask(GLboolean red, GLboolean green, GLbool
 {
     if (isContextLost())
         return;
+    if (!m_requestedAttributes.alpha() && !drawingBuffer()->isRGBTextureSupported())
+        alpha = GL_FALSE;
+
     m_colorMask[0] = red;
     m_colorMask[1] = green;
     m_colorMask[2] = blue;
@@ -2384,7 +2387,10 @@ ScriptValue WebGLRenderingContextBase::getParameter(ScriptState* scriptState, GL
     case GL_ALIASED_POINT_SIZE_RANGE:
         return getWebGLFloatArrayParameter(scriptState, pname);
     case GL_ALPHA_BITS:
-        return getIntParameter(scriptState, pname);
+        // Report 0 bits, if requested alpha attribute is false & drawingbuffer allocated as GL_RGBA
+        return (!m_requestedAttributes.alpha() && !drawingBuffer()->isRGBTextureSupported())
+            ? WebGLAny(scriptState, intZero)
+            : getIntParameter(scriptState, pname);
     case GL_ARRAY_BUFFER_BINDING:
         return WebGLAny(scriptState, PassRefPtrWillBeRawPtr<WebGLObject>(m_boundArrayBuffer.get()));
     case GL_BLEND:
@@ -2408,7 +2414,9 @@ ScriptValue WebGLRenderingContextBase::getParameter(ScriptState* scriptState, GL
     case GL_COLOR_CLEAR_VALUE:
         return getWebGLFloatArrayParameter(scriptState, pname);
     case GL_COLOR_WRITEMASK:
-        return getBooleanArrayParameter(scriptState, pname);
+        return (!m_requestedAttributes.alpha() && !drawingBuffer()->isRGBTextureSupported())
+            ? WebGLAny(scriptState, intZero)
+            : getBooleanArrayParameter(scriptState, pname);
     case GL_COMPRESSED_TEXTURE_FORMATS:
         return WebGLAny(scriptState, DOMUint32Array::create(m_compressedTextureFormats.data(), m_compressedTextureFormats.size()));
     case GL_CULL_FACE: