webgl: optimize webgl.texSubImage2D(video) path.

third_party/WebKit/Source/platform/graphics/gpu/Extensions3DUtil.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "platform/graphics/gpu/Extensions3DUtil.h"
 
 #include "public/platform/WebGraphicsContext3D.h"
 #include "wtf/text/CString.h"
 #include "wtf/text/StringHash.h"
@@ skipping 65 matching lines @@
     return m_enabledExtensions.contains(name);
 }
 
 bool Extensions3DUtil::isExtensionEnabled(const String& name)
 {
     return m_enabledExtensions.contains(name);
 }
 
 bool Extensions3DUtil::canUseCopyTextureCHROMIUM(GLenum destTarget, GLenum destFormat, GLenum destType, GLint level)
 {
-    // FIXME: restriction of (RGB || RGBA)/UNSIGNED_BYTE/(Level 0) should be lifted when
+    switch (destTarget) {
+    case GL_TEXTURE_2D:
+        break;
+    // TODO(dshwang): support cube map. crbug.com/517548

[dshwang, 2015/10/21 16:12:16]

As https://codereview.chromium.org/1275773003 was reverted, zero copy cube map
texture is not yet enabled. Let me do in another patch.

+    case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
+    case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
+    case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
+        return false;
+    default:
+        ASSERT_NOT_REACHED();
+        return false;
+    }
+    // TODO(dshwang): restriction of (RGB || RGBA)/UNSIGNED_BYTE/(Level 0) should be lifted when
     // WebGraphicsContext3D::copyTextureCHROMIUM(...) are fully functional.
-    if (destTarget == GL_TEXTURE_2D && (destFormat == GL_RGB || destFormat == GL_RGBA)
+    if ((destFormat == GL_RGB || destFormat == GL_RGBA)
         && destType == GL_UNSIGNED_BYTE
         && !level)
         return true;
     return false;
 }
 
 } // namespace blink