Drop the backbuffer on hidden tabs on GLX image transport.

content/common/gpu/image_transport_surface_linux.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 "content/common/gpu/image_transport_surface.h"
 
 // This conflicts with the defines in Xlib.h and must come first.
 #include "content/common/gpu/gpu_messages.h"
@@ skipping 94 matching lines @@
                            int32 render_view_id,
                            int32 renderer_id,
                            int32 command_buffer_id);
 
   // gfx::GLSurface implementation:
   virtual bool Initialize() OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool SwapBuffers() OVERRIDE;
   virtual gfx::Size GetSize() OVERRIDE;
   virtual bool OnMakeCurrent(gfx::GLContext* context) OVERRIDE;
+  virtual void SetVisible(bool visible) OVERRIDE;
 
  protected:
   // ImageTransportSurface implementation:
   virtual void OnNewSurfaceACK(
       uint64 surface_id, TransportDIB::Handle surface_handle) OVERRIDE;
   virtual void OnBuffersSwappedACK() OVERRIDE;
   virtual void OnResize(gfx::Size size) OVERRIDE;
 
  private:
   virtual ~GLXImageTransportSurface();
@@ skipping 329 matching lines @@
 }
 
 void GLXImageTransportSurface::ReleaseSurface() {
   DCHECK(bound_);
   GpuHostMsg_AcceleratedSurfaceRelease_Params params;
   params.identifier = window_;
   helper_->SendAcceleratedSurfaceRelease(params);
   bound_ = false;
 }
 
+void GLXImageTransportSurface::SetVisible(bool visible) {
+  Display* dpy = static_cast<Display*>(GetDisplay());
+  if (!visible) {
+    XResizeWindow(dpy, window_, 1, 1);
+  } else {
+    XResizeWindow(dpy, window_, size_.width(), size_.height());
+    needs_resize_ = true;
+  }
+  glXWaitX();
+}
+
 void GLXImageTransportSurface::OnResize(gfx::Size size) {
   TRACE_EVENT0("gpu", "GLXImageTransportSurface::OnResize");
   size_ = size;
 
   Display* dpy = static_cast<Display*>(GetDisplay());
   XResizeWindow(dpy, window_, size_.width(), size_.height());
   glXWaitX();
   needs_resize_ = true;
 }
 
@@ skipping 187 matching lines @@
       NOTREACHED();
       return NULL;
   }
   if (surface->Initialize())
     return surface;
   else
     return NULL;
 }
 
 #endif  // defined(USE_GPU)