WebGL 2: add read/write framebuffer binding points to related APIs

Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBuffer.cpp b/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 007c41bbc667e6ebc322b765ccb90b5195a5beb0..28bbeae22093322dedf1f718d45b891f57f86105 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -123,6 +123,7 @@ DrawingBuffer::DrawingBuffer(PassOwnPtr<WebGraphicsContext3D> context,
     , m_scissorEnabled(false)
     , m_texture2DBinding(0)
     , m_framebufferBinding(0)
+    , m_readFramebufferBinding(0)
     , m_activeTextureUnit(GL_TEXTURE0)
     , m_context(context)
     , m_extensionsUtil(extensionsUtil)
@@ -705,15 +706,16 @@ void DrawingBuffer::resizeDepthStencil(const IntSize& size)
 
 
 
-void DrawingBuffer::clearFramebuffers(GLbitfield clearMask)
+void DrawingBuffer::clearFramebuffers(GLenum target, GLbitfield clearMask)
 {
+    ASSERT(target == GL_FRAMEBUFFER || target == GL_DRAW_FRAMEBUFFER);
     // We will clear the multisample FBO, but we also need to clear the non-multisampled buffer.
     if (m_multisampleFBO) {
-        m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+        m_context->bindFramebuffer(target, m_fbo);
         m_context->clear(GL_COLOR_BUFFER_BIT);
     }
 
-    m_context->bindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO ? m_multisampleFBO : m_fbo);
+    m_context->bindFramebuffer(target, m_multisampleFBO ? m_multisampleFBO : m_fbo);
     m_context->clear(clearMask);
 }
 
@@ -778,11 +780,11 @@ bool DrawingBuffer::reset(const IntSize& newSize)
         m_context->stencilMaskSeparate(GL_FRONT, 0xFFFFFFFF);
     }
 
-    clearFramebuffers(clearMask);
+    clearFramebuffers(GL_FRAMEBUFFER, clearMask);
     return true;
 }
 
-void DrawingBuffer::commit()
+void DrawingBuffer::commit(GLenum target)
 {
     if (m_multisampleFBO && !m_contentsChangeCommitted) {
         m_context->bindFramebuffer(GL_READ_FRAMEBUFFER_ANGLE, m_multisampleFBO);
@@ -800,17 +802,18 @@ void DrawingBuffer::commit()
             m_context->enable(GL_SCISSOR_TEST);
     }
 
-    m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+    m_context->bindFramebuffer(target, m_fbo);
     m_contentsChangeCommitted = true;
 }
 
-void DrawingBuffer::restoreFramebufferBinding()
+void DrawingBuffer::restoreFramebufferBinding(GLenum target)
 {
-    if (!m_framebufferBinding) {
-        bind();
+    if (((target == GL_FRAMEBUFFER || target == GL_DRAW_FRAMEBUFFER) && !m_framebufferBinding)
+        || (target == GL_READ_FRAMEBUFFER && !m_readFramebufferBinding)) {
+        bind(target);
         return;
     }
-    m_context->bindFramebuffer(GL_FRAMEBUFFER, m_framebufferBinding);
+    m_context->bindFramebuffer(target, target == GL_READ_FRAMEBUFFER ? m_readFramebufferBinding : m_framebufferBinding);
 }
 
 bool DrawingBuffer::multisample() const