webgl: optimize webgl.texSubImage2D(video) path.

content/renderer/media/android/webmediaplayer_android.cc

Index: content/renderer/media/android/webmediaplayer_android.cc
diff --git a/content/renderer/media/android/webmediaplayer_android.cc b/content/renderer/media/android/webmediaplayer_android.cc
index 63f256d70d817221d6c3b13afb9b8a388e98c598..89c6ce649657396268a8061fbcdca3de830af1a3 100644
--- a/content/renderer/media/android/webmediaplayer_android.cc
+++ b/content/renderer/media/android/webmediaplayer_android.cc
@@ -634,8 +634,10 @@ void WebMediaPlayerAndroid::paint(blink::WebCanvas* canvas,
 
   unsigned textureId = static_cast<unsigned>(
     (bitmap_.getTexture())->getTextureHandle());
-  if (!copyVideoTextureToPlatformTexture(context3D, textureId,
-      GL_RGBA, GL_UNSIGNED_BYTE, true, false)) {
+  if (!copyVideoTextureToPlatformTexture(
+          context3D,
+          {CopyVideoTextureParams::FullCopy, GL_TEXTURE_2D, textureId, GL_RGBA,

[DaleCurtis, 2015/10/21 18:35:50]

Hmm, does this work by way of a C++11 initializer list? I don't remember this
working otherwise. I think you need to use a temporary "BlahBlah a = {...}"
here. 

[dshwang, 2015/10/21 19:31:07]

Yes, it's by C++11 initializer list;
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Braced_Initi...
Is it banned in chromium?

As I remember, initializer list for std::vector is banned but initializer list
for struct might be fine...

[DaleCurtis, 2015/10/22 00:35:28]

Yup, banned wholesale currently https://chromium-cpp.appspot.com/ -- see uniform
initialization syntax.

[dshwang, 2015/10/22 13:23:03]

Thanks for investigation. I replace it to constructor.

FYI, constructor in struct is allowed by coding style;
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Structs_vs._...

+           GL_UNSIGNED_BYTE, 0, 0, 0, true, false})) {
     return;
   }
 
@@ -655,12 +657,12 @@ void WebMediaPlayerAndroid::paint(blink::WebCanvas* canvas,
 
 bool WebMediaPlayerAndroid::copyVideoTextureToPlatformTexture(
     blink::WebGraphicsContext3D* web_graphics_context,
-    unsigned int texture,
-    unsigned int internal_format,
-    unsigned int type,
-    bool premultiply_alpha,
-    bool flip_y) {
+    const CopyVideoTextureParams& params) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
+  DCHECK((params.copyType == CopyVideoTextureParams::FullCopy &&
+          !params.xoffset && !params.yoffset) ||
+         (params.copyType == CopyVideoTextureParams::SubCopy &&
+          !params.internalFormat && !params.type));
   // Don't allow clients to copy an encrypted video frame.
   if (needs_external_surface_)
     return false;
@@ -691,9 +693,17 @@ bool WebMediaPlayerAndroid::copyVideoTextureToPlatformTexture(
   // value down to get the expected result.
   // flip_y==true means to reverse the video orientation while
   // flip_y==false means to keep the intrinsic orientation.
-  web_graphics_context->copyTextureCHROMIUM(
-      GL_TEXTURE_2D, src_texture, texture, internal_format, type,
-      flip_y, premultiply_alpha, false);
+  if (params.copyType == CopyVideoTextureParams::FullCopy) {
+    web_graphics_context->copyTextureCHROMIUM(
+        params.target, src_texture, params.texture, params.internalFormat,
+        params.type, params.flipY, params.premultiplyAlpha, false);
+  } else {
+    web_graphics_context->copySubTextureCHROMIUM(
+        params.target, src_texture, params.texture, params.xoffset,
+        params.yoffset, 0, 0, video_frame->natural_size().width(),
+        video_frame->natural_size().height(), params.flipY,
+        params.premultiplyAlpha, false);
+  }
 
   web_graphics_context->deleteTexture(src_texture);
   web_graphics_context->flush();