Add external surface rendering mode

cc/gl_renderer.cc

Index: cc/gl_renderer.cc
diff --git a/cc/gl_renderer.cc b/cc/gl_renderer.cc
index a40dd3a245b80e384bea0d7cce273d2d441ff6ba..8a4d7061094bdc274a1344e5e1dbd8e2f6cf59d4 100644
--- a/cc/gl_renderer.cc
+++ b/cc/gl_renderer.cc
@@ -936,6 +936,13 @@ void GLRenderer::drawStreamVideoQuad(const DrawingFrame& frame, const StreamVide
     const VideoStreamTextureProgram* program = videoStreamTextureProgram();
     setUseProgram(program->program());
 
+    if (quad->texture_id == 0) {
+        // When texture_id == 0, punch a hole instead of rendering.

[qinmin, 2012/12/17 19:34:06]

nit: fix indent

[enne (OOO), 2012/12/17 20:38:28]

What do you mean by punch a hole? Maybe I'm misunderstanding this CL, but I'm
not sure why you'd even generate a quad for this video; it sounded from the
description like you were going to composite this video external to cc.

[wonsik2, 2013/02/14 14:56:38]

It seems that 4 spaces are used throughout the file. Please follow up at
https://codereview.chromium.org/12255032/

[wonsik2, 2013/02/14 14:56:38]

Skipping a quad will make the background occlude the video composited outside of
cc. I added more comments: please follow up at
https://codereview.chromium.org/12255032/

+        GLC(m_context, m_context->blendFunc(GL_ZERO, GL_ONE_MINUS_SRC_ALPHA));
+        drawQuadGeometry(frame, quad->quadTransform(), quad->rect, program->vertexShader().matrixLocation());
+        GLC(m_context, m_context->blendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
+        return;
+    }
     toGLMatrix(&glMatrix[0], quad->matrix);
     GLC(context(), context()->uniformMatrix4fv(program->vertexShader().texMatrixLocation(), 1, false, glMatrix));