Initialize depth texture using tex{Sub}Image2D except for ANGLE ES2

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index bb2c85e8bf60d4f0e8d93d5fecae46ea2a018827..56c1716f5b2a4658240aff28bd58b5be4a30e117 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -12199,11 +12199,11 @@ bool GLES2DecoderImpl::ClearLevel(Texture* texture,
   DCHECK(target != GL_TEXTURE_3D && target != GL_TEXTURE_2D_ARRAY &&
          target != GL_TEXTURE_EXTERNAL_OES);
   uint32_t channels = GLES2Util::GetChannelsForFormat(format);
-  if ((feature_info_->feature_flags().angle_depth_texture ||
-       feature_info_->IsWebGL2OrES3Context())
-      && (channels & GLES2Util::kDepth) != 0) {
+  if ((channels & GLES2Util::kDepth) != 0 &&
+      feature_info_->feature_flags().angle_depth_texture &&
+      feature_info_->gl_version_info().is_es2) {

[Kai Ninomiya, 2016/11/17 20:41:22]

I think the logic here is valid but doesn't quite make sense. If
angle_depth_texture is false, I think neither path will work. Perhaps it should
throw an error in that case:

if ((channels & GLES2Util::kDepth) != 0 &&
    !feature_info_->feature_flags().angle_depth_texture) {
  // this is an error
}

if ((channels & GLES2Util::kDepth) != 0 &&
    feature_info_->gl_version_info().is_es2) {

[Zhenyao Mo, 2016/11/17 20:46:58]

You are right.  I can move feature_info_->feature_flags().angle_depth_texture
into the if body as a DCHECK

     // It's a depth format and ANGLE doesn't allow texImage2D or texSubImage2D
-    // on depth formats.
+    // on depth formats in ES2.
     GLuint fb = 0;
     glGenFramebuffersEXT(1, &fb);
     glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fb);