Add WebGraphicsContext support for readbacks from any framebuffer.

webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc

 // Copyright (c) 2011 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.
 
 #if defined(ENABLE_GPU)
 
 #include "webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h"
 
 #include <GLES2/gl2.h>
 #ifndef GL_GLEXT_PROTOTYPES
@@ skipping 798 matching lines @@
     // creation attributes.
     memcpy(scanline, row_b, row_bytes);
     memcpy(row_b, row_a, row_bytes);
     memcpy(row_a, scanline, row_bytes);
   }
 }
 #endif
 
 bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
     unsigned char* pixels,
-    size_t buffer_size) {
+    int width,
+    int height,
+    size_t buffer_size,
+    WebGLId framebuffer) {
   // TODO(gmam): See if we can comment this in.
   // ClearContext();
-  if (buffer_size != static_cast<size_t>(4 * width() * height())) {
+  if (buffer_size != static_cast<size_t>(4 * width * height)) {
     return false;
   }
 
   // Earlier versions of this code used the GPU to flip the
   // framebuffer vertically before reading it back for compositing
   // via software. This code was quite complicated, used a lot of
   // GPU memory, and didn't provide an obvious speedup. Since this
   // vertical flip is only a temporary solution anyway until Chrome
   // is fully GPU composited, it wasn't worth the complexity.
 
-  bool mustRestoreFBO = (bound_fbo_ != 0);
+  bool mustRestoreFBO = (bound_fbo_ != framebuffer);
   if (mustRestoreFBO) {
-    gl_->BindFramebuffer(GL_FRAMEBUFFER, 0);
+    gl_->BindFramebuffer(GL_FRAMEBUFFER, framebuffer);
   }
-   gl_->ReadPixels(0, 0, cached_width_, cached_height_,
+   gl_->ReadPixels(0, 0, width, height,
                    GL_RGBA, GL_UNSIGNED_BYTE, pixels);
 
   // Swizzle red and blue channels
   // TODO(kbr): expose GL_BGRA as extension
   for (size_t i = 0; i < buffer_size; i += 4) {
     std::swap(pixels[i], pixels[i + 2]);
   }
 
   if (mustRestoreFBO) {
     gl_->BindFramebuffer(GL_FRAMEBUFFER, bound_fbo_);
   }
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   if (pixels) {
-    FlipVertically(pixels, cached_width_, cached_height_);
+    FlipVertically(pixels, width, height);
   }
 #endif
 
   return true;
 }
 
+bool WebGraphicsContext3DInProcessCommandBufferImpl::readBackFramebuffer(
+    unsigned char* pixels,
+    size_t buffer_size) {
+  return readBackFramebuffer(pixels, width(), height(), buffer_size, 0);
+}
+
 void WebGraphicsContext3DInProcessCommandBufferImpl::synthesizeGLError(
     WGC3Denum error) {
   if (find(synthetic_errors_.begin(), synthetic_errors_.end(), error) ==
       synthetic_errors_.end()) {
     synthetic_errors_.push_back(error);
   }
 }
 
 void* WebGraphicsContext3DInProcessCommandBufferImpl::mapBufferSubDataCHROMIUM(
     WGC3Denum target,
@@ skipping 752 matching lines @@
   if (context_lost_callback_) {
     context_lost_callback_->onContextLost();
   }
 }
 
 }  // namespace gpu
 }  // namespace webkit
 
 #endif  // defined(ENABLE_GPU)