WebGL 2: add readPixels API to read pixels into pixel pack buffer

Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index 8c61c89da95560926cbff64fb2e0759630ec2f9e..5d1887ff64a0a2b87bd46fb36179cd2409626ce5 100644
--- a/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -49,7 +49,6 @@ WebGL2RenderingContextBase::~WebGL2RenderingContextBase()
 
     m_boundCopyReadBuffer = nullptr;
     m_boundCopyWriteBuffer = nullptr;
-    m_boundPixelPackBuffer = nullptr;
     m_boundPixelUnpackBuffer = nullptr;
     m_boundTransformFeedbackBuffer = nullptr;
     m_boundUniformBuffer = nullptr;
@@ -67,7 +66,6 @@ void WebGL2RenderingContextBase::initializeNewContext()
 
     m_boundCopyReadBuffer = nullptr;
     m_boundCopyWriteBuffer = nullptr;
-    m_boundPixelPackBuffer = nullptr;
     m_boundPixelUnpackBuffer = nullptr;
     m_boundTransformFeedbackBuffer = nullptr;
     m_boundUniformBuffer = nullptr;