Fix transform feedback bugs

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index de0568a5dc1e9c93b40a66087efe5ba3414aa34b..7f03e50f6f215d40ad68be3596bbe7cd7028eecb 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -2006,6 +2006,10 @@ WebGLTransformFeedback* WebGL2RenderingContextBase::createTransformFeedback()
 
 void WebGL2RenderingContextBase::deleteTransformFeedback(WebGLTransformFeedback* feedback)
 {
+    if (transformFeedbackActive()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "deleteTransformFeedback", "transform feedback is active");
+        return;
+    }
     if (feedback == m_transformFeedbackBinding)
         m_transformFeedbackBinding = nullptr;
 
@@ -2226,6 +2230,7 @@ void WebGL2RenderingContextBase::bindBufferBase(GLenum target, GLuint index, Web
     }
 
     webContext()->bindBufferBase(target, index, objectOrZero(buffer));
+    webContext()->bindBuffer(target, objectOrZero(buffer));

[Zhenyao Mo, 2016/03/01 22:33:01]

I am not sure this is the right fix.

I don't think we need to explicitly call bindBuffer(), because bindBufferBase()
should take care of that.  So it's either a driver bug (I doubt it), or there
are some place in Chrome we fail to change the cached bound buffer. That is the
bug we need to fix.

[qiankun, 2016/03/01 23:52:06]

The driver really call bindBuffer() when do bindBuferBase(). But Chrome didn't
change the cached bound buffer, so bindBuffer() may be not called to driver. See
commit log in https://github.com/KhronosGroup/WebGL/pull/1513. 

bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer); // buffer_in_driver = buffer
buffer_chaced_by_chrome = buffer
bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, null);// buffer_in_driver = null
buffer_chaced_by_chrome = buffer
bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer); // buffer_in_driver = null
buffer_chaced_by_chrome = buffer;  Between two calls of
"bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer);"
bound_transform_feedback_buffer_ doesn't change, so
GLES2Implementation::BindBufferHelper doesn't issue bindBuffer to
command buffer server side. 

 }
 
 void WebGL2RenderingContextBase::bindBufferRange(GLenum target, GLuint index, WebGLBuffer* buffer, long long offset, long long size)