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

Source/modules/webgl/WebGL2RenderingContextBase.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebGL2RenderingContextBase_h
 #define WebGL2RenderingContextBase_h
 
 #include "modules/webgl/WebGLExtension.h"
 #include "modules/webgl/WebGLRenderingContextBase.h"
 
@@ skipping 140 matching lines @@
     ScriptValue getActiveUniformBlockParameter(ScriptState*, WebGLProgram*, GLuint, GLenum);
     String getActiveUniformBlockName(WebGLProgram*, GLuint);
     void uniformBlockBinding(WebGLProgram*, GLuint, GLuint);
 
     /* Vertex Array Objects */
     WebGLVertexArrayObject* createVertexArray();
     void deleteVertexArray(WebGLVertexArrayObject*);
     GLboolean isVertexArray(WebGLVertexArrayObject*);
     void bindVertexArray(WebGLVertexArrayObject*);
 
+    /* Reading */
+    void readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, long long offset);
+
     /* WebGLRenderingContextBase overrides */
     void initializeNewContext() override;
     void bindFramebuffer(GLenum target, WebGLFramebuffer*) override;
     void deleteFramebuffer(WebGLFramebuffer*) override;
     ScriptValue getParameter(ScriptState*, GLenum pname) override;
     ScriptValue getTexParameter(ScriptState*, GLenum target, GLenum pname) override;
     ScriptValue getFramebufferAttachmentParameter(ScriptState*, GLenum target, GLenum attachment, GLenum pname) override;
+    void readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, DOMArrayBufferView* pixels) override;
     void restoreCurrentFramebuffer() override;
 
     EAGERLY_FINALIZE();
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     WebGL2RenderingContextBase(HTMLCanvasElement*, PassOwnPtr<WebGraphicsContext3D>, const WebGLContextAttributes& requestedAttributes);
 
     // Helper function to validate target and the attachment combination for getFramebufferAttachmentParameters.
     // Generate GL error and return false if parameters are illegal.
@@ skipping 48 matching lines @@
     PersistentHeapVectorWillBeHeapVector<Member<WebGLSampler>> m_samplerUnits;
 };
 
 DEFINE_TYPE_CASTS(WebGL2RenderingContextBase, CanvasRenderingContext, context,
     context->is3d() && WebGLRenderingContextBase::getWebGLVersion(context) >= 2,
     context.is3d() && WebGLRenderingContextBase::getWebGLVersion(&context) >= 2);
 
 } // namespace blink
 
 #endif