Reland 81998.The bug in webkit\gpu\webgraphicscontext3d_in_process_impl.cc that assumed creating a new GLContext made it current is now fixed and this patch should now work.

Original message:

Split OSMesa implementations of *GLContext into GLContextOSMesa and *GLSurfaceOSMesa.

Surfaces are independent of contexts in GL. To facilitate sharing of surfaces between processes, I have separated them from the notion of contexts because contexts cannot be shared between processes.

I started with EGL in r81512 and WGL in r81807. This is the same thing for OSMesa.

GLContextOSMesa still has a pointer to a surface and still has some surface specific operations that just forward through to it. Once I have refactored all the GLContext implementations in this way, I will remove these pointers and the surface specific opertations.

There will not be "view" and "offscreen" GL contexts. Rather there will be a single context type for each backend which can be made current with a surface that directs output either to a view or offscreen surface.

Original review:
http://codereview.chromium.org/6864031/

TEST=ran linux_layout and mac_layout try jobs (they were failing before)
BUG=none
Review URL: http://codereview.chromium.org/6881071

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@82748 0039d316-1c4b-4281-b951-d872f2087c98

9 files changed, 240 insertions, 210 deletions

diff --git a/ui/gfx/gl/gl.gyp b/ui/gfx/gl/gl.gyp
index 507d9b4..83299b3a 100644
--- a/ui/gfx/gl/gl.gyp
+++ b/ui/gfx/gl/gl.gyp
@@ -76,6 +76,8 @@
         'gl_interface.h',
         'gl_surface.cc',
         'gl_surface.h',
+        'gl_surface_osmesa.cc',
+        'gl_surface_osmesa.h',
         'gl_switches.cc',
         'gl_switches.h',
         '<(gl_binding_output_dir)/gl_bindings_autogen_gl.cc',
diff --git a/ui/gfx/gl/gl_context_linux.cc b/ui/gfx/gl/gl_context_linux.cc
index 6cd77dd..36f0e8a 100644
--- a/ui/gfx/gl/gl_context_linux.cc
+++ b/ui/gfx/gl/gl_context_linux.cc
@@ -22,6 +22,7 @@ extern "C" {
 #include "ui/gfx/gl/gl_context_stub.h"
 #include "ui/gfx/gl/gl_implementation.h"
 #include "ui/gfx/gl/gl_surface_egl.h"
+#include "ui/gfx/gl/gl_surface_osmesa.h"
 
 namespace {
 
@@ -77,29 +78,20 @@ class ViewGLContext : public BaseLinuxGLContext {
   DISALLOW_COPY_AND_ASSIGN(ViewGLContext);
 };
 
-// This class is a wrapper around a GL context that uses OSMesa to render
-// to an offscreen buffer and then blits it to a window.
-class OSMesaViewGLContext : public GLContext {
+// This OSMesa GL surface can use XLib to swap the contents of the buffer to a
+// view.
+class NativeViewGLSurfaceOSMesa : public GLSurfaceOSMesa {
  public:
-  explicit OSMesaViewGLContext(gfx::PluginWindowHandle window)
-      : window_graphics_context_(0),
-        window_(window),
-        pixmap_graphics_context_(0),
-        pixmap_(0) {
-    DCHECK(window);
-  }
+  explicit NativeViewGLSurfaceOSMesa(gfx::PluginWindowHandle window);
+  virtual ~NativeViewGLSurfaceOSMesa();
 
   // Initializes the GL context.
   bool Initialize();
 
+  // Implement a subset of GLSurface.
   virtual void Destroy();
-  virtual bool MakeCurrent();
-  virtual bool IsCurrent();
   virtual bool IsOffscreen();
   virtual bool SwapBuffers();
-  virtual gfx::Size GetSize();
-  virtual void* GetHandle();
-  virtual void SetSwapInterval(int interval);
 
  private:
   bool UpdateSize();
@@ -108,9 +100,8 @@ class OSMesaViewGLContext : public GLContext {
   gfx::PluginWindowHandle window_;
   GC pixmap_graphics_context_;
   Pixmap pixmap_;
-  OSMesaGLContext osmesa_context_;
 
-  DISALLOW_COPY_AND_ASSIGN(OSMesaViewGLContext);
+  DISALLOW_COPY_AND_ASSIGN(NativeViewGLSurfaceOSMesa);
 };
 
 // This class is a wrapper around a GL context used for offscreen rendering.
@@ -348,13 +339,20 @@ void ViewGLContext::SetSwapInterval(int interval) {
   }
 }
 
-bool OSMesaViewGLContext::Initialize() {
-  if (!osmesa_context_.Initialize(OSMESA_BGRA, NULL)) {
-    LOG(ERROR) << "OSMesaGLContext::Initialize failed.";
-    Destroy();
-    return false;
-  }
+NativeViewGLSurfaceOSMesa::NativeViewGLSurfaceOSMesa(
+    gfx::PluginWindowHandle window)
+  : window_graphics_context_(0),
+    window_(window),
+    pixmap_graphics_context_(0),
+    pixmap_(0) {
+  DCHECK(window);
+}
 
+NativeViewGLSurfaceOSMesa::~NativeViewGLSurfaceOSMesa() {
+  Destroy();
+}
+
+bool NativeViewGLSurfaceOSMesa::Initialize() {
   window_graphics_context_ = XCreateGC(GetXDisplayHelper(),
                                        window_,
                                        0,
@@ -370,9 +368,7 @@ bool OSMesaViewGLContext::Initialize() {
   return true;
 }
 
-void OSMesaViewGLContext::Destroy() {
-  osmesa_context_.Destroy();
-
+void NativeViewGLSurfaceOSMesa::Destroy() {
   Display* display = GetXDisplayHelper();
 
   if (pixmap_graphics_context_) {
@@ -391,31 +387,19 @@ void OSMesaViewGLContext::Destroy() {
   }
 }
 
-bool OSMesaViewGLContext::MakeCurrent() {
-  // TODO(apatrick): This is a bit of a hack. The window might have had zero
-  // size when the context was initialized. Assume it has a valid size when
-  // MakeCurrent is called and resize the back buffer if necessary.
-  UpdateSize();
-  return osmesa_context_.MakeCurrent();
-}
-
-bool OSMesaViewGLContext::IsCurrent() {
-  return osmesa_context_.IsCurrent();
-}
-
-bool OSMesaViewGLContext::IsOffscreen() {
+bool NativeViewGLSurfaceOSMesa::IsOffscreen() {
   return false;
 }
 
-bool OSMesaViewGLContext::SwapBuffers() {
+bool NativeViewGLSurfaceOSMesa::SwapBuffers() {
   // Update the size before blitting so that the blit size is exactly the same
   // as the window.
   if (!UpdateSize()) {
-    LOG(ERROR) << "Failed to update size of OSMesaGLContext.";
+    LOG(ERROR) << "Failed to update size of GLContextOSMesa.";
     return false;
   }
 
-  gfx::Size size = osmesa_context_.GetSize();
+  gfx::Size size = GetSize();
 
   Display* display = GetXDisplayHelper();
 
@@ -427,7 +411,7 @@ bool OSMesaViewGLContext::SwapBuffers() {
                    attributes.depth,
                    pixmap_,
                    pixmap_graphics_context_,
-                   static_cast<const uint8*>(osmesa_context_.buffer()),
+                   static_cast<const uint8*>(GetHandle()),
                    size.width(),
                    size.height());
 
@@ -443,21 +427,7 @@ bool OSMesaViewGLContext::SwapBuffers() {
   return true;
 }
 
-gfx::Size OSMesaViewGLContext::GetSize() {
-  return osmesa_context_.GetSize();
-}
-
-void* OSMesaViewGLContext::GetHandle() {
-  return osmesa_context_.GetHandle();
-}
-
-void OSMesaViewGLContext::SetSwapInterval(int interval) {
-  DCHECK(IsCurrent());
-  // Fail silently. It is legitimate to set the swap interval on a view context
-  // but XLib does not have those semantics.
-}
-
-bool OSMesaViewGLContext::UpdateSize() {
+bool NativeViewGLSurfaceOSMesa::UpdateSize() {
   // Get the window size.
   XWindowAttributes attributes;
   Display* display = GetXDisplayHelper();
@@ -466,12 +436,12 @@ bool OSMesaViewGLContext::UpdateSize() {
                                     std::max(1, attributes.height));
 
   // Early out if the size has not changed.
-  gfx::Size osmesa_size = osmesa_context_.GetSize();
+  gfx::Size osmesa_size = GetSize();
   if (pixmap_graphics_context_ && pixmap_ && window_size == osmesa_size)
     return true;
 
   // Change osmesa surface size to that of window.
-  osmesa_context_.Resize(window_size);
+  Resize(window_size);
 
   // Destroy the previous pixmap and graphics context.
   if (pixmap_graphics_context_) {
@@ -529,9 +499,14 @@ GLContext* GLContext::CreateViewGLContext(gfx::PluginWindowHandle window,
       return context.release();
     }
     case kGLImplementationOSMesaGL: {
-      scoped_ptr<OSMesaViewGLContext> context(new OSMesaViewGLContext(window));
+      scoped_ptr<NativeViewGLSurfaceOSMesa> surface(
+          new NativeViewGLSurfaceOSMesa(window));
+      if (!surface->Initialize())
+        return NULL;
 
-      if (!context->Initialize())
+      scoped_ptr<GLContextOSMesa> context(
+          new GLContextOSMesa(surface.release()));
+      if (!context->Initialize(OSMESA_BGRA, NULL))
         return NULL;
 
       return context.release();
@@ -823,8 +798,12 @@ GLContext* GLContext::CreateOffscreenGLContext(GLContext* shared_context) {
       return context.release();
     }
     case kGLImplementationOSMesaGL: {
-      scoped_ptr<OSMesaGLContext> context(new OSMesaGLContext);
-      if (!context->Initialize(OSMESA_RGBA, shared_context))
+      scoped_ptr<GLSurfaceOSMesa> surface(new GLSurfaceOSMesa());
+      surface->Resize(gfx::Size(1, 1));
+
+      scoped_ptr<GLContextOSMesa> context(
+          new GLContextOSMesa(surface.release()));
+      if (!context->Initialize(OSMESA_BGRA, shared_context))
         return NULL;
 
       return context.release();
diff --git a/ui/gfx/gl/gl_context_mac.cc b/ui/gfx/gl/gl_context_mac.cc
index 10e8bf3..21b0403 100644
--- a/ui/gfx/gl/gl_context_mac.cc
+++ b/ui/gfx/gl/gl_context_mac.cc
@@ -192,7 +192,11 @@ GLContext* GLContext::CreateOffscreenGLContext(GLContext* shared_context) {
       return context.release();
     }
     case kGLImplementationOSMesaGL: {
-      scoped_ptr<OSMesaGLContext> context(new OSMesaGLContext);
+      scoped_ptr<GLSurfaceOSMesa> surface(new GLSurfaceOSMesa());
+      surface->Resize(gfx::Size(1, 1));
+
+      scoped_ptr<GLContextOSMesa> context(
+          new GLContextOSMesa(surface.release()));
       if (!context->Initialize(OSMESA_RGBA, shared_context))
         return NULL;
 
diff --git a/ui/gfx/gl/gl_context_osmesa.cc b/ui/gfx/gl/gl_context_osmesa.cc
index 9d1e802..6da01d1 100644
--- a/ui/gfx/gl/gl_context_osmesa.cc
+++ b/ui/gfx/gl/gl_context_osmesa.cc
@@ -12,19 +12,18 @@
 
 namespace gfx {
 
-OSMesaGLContext::OSMesaGLContext() : context_(NULL)
+GLContextOSMesa::GLContextOSMesa(GLSurfaceOSMesa* surface)
+    : surface_(surface),
+      context_(NULL)
 {
 }
 
-OSMesaGLContext::~OSMesaGLContext() {
+GLContextOSMesa::~GLContextOSMesa() {
 }
 
-bool OSMesaGLContext::Initialize(GLuint format, GLContext* shared_context) {
+bool GLContextOSMesa::Initialize(GLuint format, GLContext* shared_context) {
   DCHECK(!context_);
 
-  size_ = gfx::Size(1, 1);
-  buffer_.reset(new int32[1]);
-
   OSMesaContext shared_handle = NULL;
   if (shared_context)
     shared_handle = static_cast<OSMesaContext>(shared_context->GetHandle());
@@ -39,93 +38,64 @@ bool OSMesaGLContext::Initialize(GLuint format, GLContext* shared_context) {
     return false;
   }
 
-  if (!MakeCurrent()) {
-    LOG(ERROR) << "MakeCurrent failed.";
-    Destroy();
-    return false;
-  }
-
-  // Row 0 is at the top.
-  OSMesaPixelStore(OSMESA_Y_UP, 0);
-
-  if (!InitializeCommon()) {
-    LOG(ERROR) << "GLContext::InitializeCommon failed.";
-    Destroy();
-    return false;
-  }
-
   return true;
 }
 
-void OSMesaGLContext::Resize(const gfx::Size& new_size) {
-  if (new_size == size_)
-    return;
-
-  // Allocate a new back buffer.
-  scoped_array<int32> new_buffer(new int32[new_size.GetArea()]);
-  memset(new_buffer.get(), 0, new_size.GetArea() * sizeof(new_buffer[0]));
-
-  // Copy the current back buffer into the new buffer.
-  int copy_width = std::min(size_.width(), new_size.width());
-  int copy_height = std::min(size_.height(), new_size.height());
-  for (int y = 0; y < copy_height; ++y) {
-    for (int x = 0; x < copy_width; ++x) {
-      new_buffer[y * new_size.width() + x] = buffer_[y * size_.width() + x];
-    }
-  }
-
-  buffer_.reset(new_buffer.release());
-  size_ = new_size;
-
-  // If this context is current, need to call MakeCurrent again so OSMesa uses
-  // the new buffer.
-  if (IsCurrent())
-    MakeCurrent();
-}
-
-void OSMesaGLContext::Destroy() {
+void GLContextOSMesa::Destroy() {
   if (context_) {
     OSMesaDestroyContext(static_cast<OSMesaContext>(context_));
     context_ = NULL;
   }
-  buffer_.reset();
-  size_ = gfx::Size();
+
+  surface_->Destroy();
+  surface_.reset();
 }
 
-bool OSMesaGLContext::MakeCurrent() {
+bool GLContextOSMesa::MakeCurrent() {
   DCHECK(context_);
-  return OSMesaMakeCurrent(static_cast<OSMesaContext>(context_),
-                           buffer_.get(),
-                           GL_UNSIGNED_BYTE,
-                           size_.width(), size_.height()) == GL_TRUE;
+
+  gfx::Size size = surface_->GetSize();
+
+  if (!OSMesaMakeCurrent(static_cast<OSMesaContext>(context_),
+                         surface_->GetHandle(),
+                         GL_UNSIGNED_BYTE,
+                         size.width(), size.height())) {
+    return false;
+  }
+
+  // Row 0 is at the top.
+  OSMesaPixelStore(OSMESA_Y_UP, 0);
+
   return true;
 }
 
-bool OSMesaGLContext::IsCurrent() {
+bool GLContextOSMesa::IsCurrent() {
   DCHECK(context_);
   return context_ == OSMesaGetCurrentContext();
 }
 
-bool OSMesaGLContext::IsOffscreen() {
-  return true;
+bool GLContextOSMesa::IsOffscreen() {
+  // TODO(apatrick): remove this from GLContext interface.
+  return surface_->IsOffscreen();
 }
 
-bool OSMesaGLContext::SwapBuffers() {
-  NOTREACHED() << "Should not call SwapBuffers on an OSMesaGLContext.";
-  return false;
+bool GLContextOSMesa::SwapBuffers() {
+  // TODO(apatrick): remove this from GLContext interface.
+  return surface_->SwapBuffers();
 }
 
-gfx::Size OSMesaGLContext::GetSize() {
-  return size_;
+gfx::Size GLContextOSMesa::GetSize() {
+  // TODO(apatrick): remove this from GLContext interface.
+  return surface_->GetSize();
 }
 
-void* OSMesaGLContext::GetHandle() {
+void* GLContextOSMesa::GetHandle() {
   return context_;
 }
 
-void OSMesaGLContext::SetSwapInterval(int interval) {
+void GLContextOSMesa::SetSwapInterval(int interval) {
   DCHECK(IsCurrent());
-  NOTREACHED() << "Attempt to call SetSwapInterval on an OSMesaGLContext.";
+  NOTREACHED() << "Attempt to call SetSwapInterval on an GLContextOSMesa.";
 }
 
 }  // namespace gfx
diff --git a/ui/gfx/gl/gl_context_osmesa.h b/ui/gfx/gl/gl_context_osmesa.h
index 77ca820..33aa21c 100644
--- a/ui/gfx/gl/gl_context_osmesa.h
+++ b/ui/gfx/gl/gl_context_osmesa.h
@@ -8,6 +8,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/gl/gl_context.h"
+#include "ui/gfx/gl/gl_surface_osmesa.h"
 #include "ui/gfx/size.h"
 
 typedef struct osmesa_context *OSMesaContext;
@@ -15,22 +16,14 @@ typedef struct osmesa_context *OSMesaContext;
 namespace gfx {
 
 // Encapsulates an OSMesa OpenGL context that uses software rendering.
-class OSMesaGLContext : public GLContext {
+class GLContextOSMesa : public GLContext {
  public:
-  OSMesaGLContext();
-  virtual ~OSMesaGLContext();
+  explicit GLContextOSMesa(GLSurfaceOSMesa* surface);
+  virtual ~GLContextOSMesa();
 
-  // Initialize an OSMesa GL context with the default 1 x 1 initial size.
+  // Initialize an OSMesa GL context.
   bool Initialize(GLuint format, GLContext* shared_context);
 
-  // Resize the back buffer, preserving the old content. Does nothing if the
-  // size is unchanged.
-  void Resize(const gfx::Size& new_size);
-
-  const void* buffer() const {
-    return buffer_.get();
-  }
-
   // Implement GLContext.
   virtual void Destroy();
   virtual bool MakeCurrent();
@@ -42,11 +35,10 @@ class OSMesaGLContext : public GLContext {
   virtual void SetSwapInterval(int interval);
 
  private:
-  gfx::Size size_;
-  scoped_array<int32> buffer_;
+  scoped_ptr<GLSurfaceOSMesa> surface_;
   OSMesaContext context_;
 
-  DISALLOW_COPY_AND_ASSIGN(OSMesaGLContext);
+  DISALLOW_COPY_AND_ASSIGN(GLContextOSMesa);
 };
 
 }  // namespace gfx
diff --git a/ui/gfx/gl/gl_context_win.cc b/ui/gfx/gl/gl_context_win.cc
index 87f3d98..3222b84 100644
--- a/ui/gfx/gl/gl_context_win.cc
+++ b/ui/gfx/gl/gl_context_win.cc
@@ -19,40 +19,33 @@
 #include "ui/gfx/gl/gl_context_wgl.h"
 #include "ui/gfx/gl/gl_implementation.h"
 #include "ui/gfx/gl/gl_surface_egl.h"
+#include "ui/gfx/gl/gl_surface_osmesa.h"
 #include "ui/gfx/gl/gl_surface_wgl.h"
 
 namespace gfx {
 
-// This class is a wrapper around a GL context that uses OSMesa to render
-// to an offscreen buffer and then blits it to a window.
-class OSMesaViewGLContext : public GLContext {
+// This OSMesa GL surface can use GDI to swap the contents of the buffer to a
+// view.
+class NativeViewGLSurfaceOSMesa : public GLSurfaceOSMesa {
  public:
-  explicit OSMesaViewGLContext(gfx::PluginWindowHandle window)
-      : window_(window),
-        device_context_(NULL) {
-    DCHECK(window);
-  }
+  explicit NativeViewGLSurfaceOSMesa(gfx::PluginWindowHandle window);
+  virtual ~NativeViewGLSurfaceOSMesa();
 
   // Initializes the GL context.
   bool Initialize();
 
+  // Implement subset of GLSurface.
   virtual void Destroy();
-  virtual bool MakeCurrent();
-  virtual bool IsCurrent();
   virtual bool IsOffscreen();
   virtual bool SwapBuffers();
-  virtual gfx::Size GetSize();
-  virtual void* GetHandle();
-  virtual void SetSwapInterval(int interval);
 
  private:
   void UpdateSize();
 
   gfx::PluginWindowHandle window_;
   HDC device_context_;
-  OSMesaGLContext osmesa_context_;
 
-  DISALLOW_COPY_AND_ASSIGN(OSMesaViewGLContext);
+  DISALLOW_COPY_AND_ASSIGN(NativeViewGLSurfaceOSMesa);
 };
 
 // Helper routine that does one-off initialization like determining the
@@ -93,55 +86,45 @@ bool GLContext::InitializeOneOff() {
   return true;
 }
 
-bool OSMesaViewGLContext::Initialize() {
-  // The GL context will render to this window.
-  device_context_ = GetDC(window_);
+NativeViewGLSurfaceOSMesa::NativeViewGLSurfaceOSMesa(
+    gfx::PluginWindowHandle window)
+  : window_(window),
+    device_context_(NULL) {
+  DCHECK(window);
+}
 
-  if (!osmesa_context_.Initialize(OSMESA_RGBA, NULL)) {
-    LOG(ERROR) << "OSMesaGLContext::Initialize failed.";
-    Destroy();
-    return false;
-  }
+NativeViewGLSurfaceOSMesa::~NativeViewGLSurfaceOSMesa() {
+  Destroy();
+}
 
+bool NativeViewGLSurfaceOSMesa::Initialize() {
+  device_context_ = GetDC(window_);
   UpdateSize();
-
   return true;
 }
 
-void OSMesaViewGLContext::Destroy() {
-  osmesa_context_.Destroy();
-
+void NativeViewGLSurfaceOSMesa::Destroy() {
   if (window_ && device_context_)
     ReleaseDC(window_, device_context_);
 
   window_ = NULL;
   device_context_ = NULL;
-}
 
-bool OSMesaViewGLContext::MakeCurrent() {
-  // TODO(apatrick): This is a bit of a hack. The window might have had zero
-  // size when the context was initialized. Assume it has a valid size when
-  // MakeCurrent is called and resize the back buffer if necessary.
-  UpdateSize();
-  return osmesa_context_.MakeCurrent();
+  GLSurfaceOSMesa::Destroy();
 }
 
-bool OSMesaViewGLContext::IsCurrent() {
-  return osmesa_context_.IsCurrent();
-}
-
-bool OSMesaViewGLContext::IsOffscreen() {
+bool NativeViewGLSurfaceOSMesa::IsOffscreen() {
   return false;
 }
 
-bool OSMesaViewGLContext::SwapBuffers() {
+bool NativeViewGLSurfaceOSMesa::SwapBuffers() {
   DCHECK(device_context_);
 
   // Update the size before blitting so that the blit size is exactly the same
   // as the window.
   UpdateSize();
 
-  gfx::Size size = osmesa_context_.GetSize();
+  gfx::Size size = GetSize();
 
   // Note: negating the height below causes GDI to treat the bitmap data as row
   // 0 being at the top.
@@ -166,7 +149,7 @@ bool OSMesaViewGLContext::SwapBuffers() {
   StretchDIBits(device_context_,
                 0, 0, size.width(), size.height(),
                 0, 0, size.width(), size.height(),
-                osmesa_context_.buffer(),
+                GetHandle(),
                 reinterpret_cast<BITMAPINFO*>(&info),
                 DIB_RGB_COLORS,
                 SRCCOPY);
@@ -174,21 +157,7 @@ bool OSMesaViewGLContext::SwapBuffers() {
   return true;
 }
 
-gfx::Size OSMesaViewGLContext::GetSize() {
-  return osmesa_context_.GetSize();
-}
-
-void* OSMesaViewGLContext::GetHandle() {
-  return osmesa_context_.GetHandle();
-}
-
-void OSMesaViewGLContext::SetSwapInterval(int interval) {
-  DCHECK(IsCurrent());
-  // Fail silently. It is legitimate to set the swap interval on a view context
-  // but GDI does not have those semantics.
-}
-
-void OSMesaViewGLContext::UpdateSize() {
+void NativeViewGLSurfaceOSMesa::UpdateSize() {
   // Change back buffer size to that of window. If window handle is invalid, do
   // not change the back buffer size.
   RECT rect;
@@ -198,15 +167,21 @@ void OSMesaViewGLContext::UpdateSize() {
   gfx::Size window_size = gfx::Size(
     std::max(1, static_cast<int>(rect.right - rect.left)),
     std::max(1, static_cast<int>(rect.bottom - rect.top)));
-  osmesa_context_.Resize(window_size);
+  Resize(window_size);
 }
 
 GLContext* GLContext::CreateViewGLContext(gfx::PluginWindowHandle window,
                                           bool multisampled) {
   switch (GetGLImplementation()) {
     case kGLImplementationOSMesaGL: {
-      scoped_ptr<OSMesaViewGLContext> context(new OSMesaViewGLContext(window));
-      if (!context->Initialize())
+      scoped_ptr<NativeViewGLSurfaceOSMesa> surface(
+          new NativeViewGLSurfaceOSMesa(window));
+      if (!surface->Initialize())
+        return NULL;
+
+      scoped_ptr<GLContextOSMesa> context(
+          new GLContextOSMesa(surface.release()));
+      if (!context->Initialize(OSMESA_RGBA, NULL))
         return NULL;
 
       return context.release();
@@ -248,7 +223,11 @@ GLContext* GLContext::CreateViewGLContext(gfx::PluginWindowHandle window,
 GLContext* GLContext::CreateOffscreenGLContext(GLContext* shared_context) {
   switch (GetGLImplementation()) {
     case kGLImplementationOSMesaGL: {
-      scoped_ptr<OSMesaGLContext> context(new OSMesaGLContext);
+      scoped_ptr<GLSurfaceOSMesa> surface(new GLSurfaceOSMesa());
+      surface->Resize(gfx::Size(1, 1));
+
+      scoped_ptr<GLContextOSMesa> context(
+          new GLContextOSMesa(surface.release()));
       if (!context->Initialize(OSMESA_RGBA, shared_context))
         return NULL;
 
diff --git a/ui/gfx/gl/gl_surface_egl.h b/ui/gfx/gl/gl_surface_egl.h
index 9ff1c2b..fe31494 100644
--- a/ui/gfx/gl/gl_surface_egl.h
+++ b/ui/gfx/gl/gl_surface_egl.h
@@ -15,7 +15,7 @@ typedef void* EGLSurface;
 
 namespace gfx {
 
-// Interface for EGL contexts.
+// Interface for EGL surface.
 class GLSurfaceEGL : public GLSurface {
  public:
   GLSurfaceEGL();
@@ -35,7 +35,7 @@ class NativeViewGLSurfaceEGL : public GLSurfaceEGL {
   explicit NativeViewGLSurfaceEGL(void* window);
   virtual ~NativeViewGLSurfaceEGL();
 
-  // Initialize an EGL context.
+  // Initialize an EGL surface.
   bool Initialize();
 
   // Implement GLSurface.
@@ -58,7 +58,7 @@ class PbufferGLSurfaceEGL : public GLSurfaceEGL {
   explicit PbufferGLSurfaceEGL(const gfx::Size& size);
   virtual ~PbufferGLSurfaceEGL();
 
-  // Initialize an EGL context that shares a namespace with another.
+  // Initialize an EGL surface.
   bool Initialize();
 
   // Implement GLSurface.
diff --git a/ui/gfx/gl/gl_surface_osmesa.cc b/ui/gfx/gl/gl_surface_osmesa.cc
new file mode 100644
index 0000000..8c4d11d
--- /dev/null
+++ b/ui/gfx/gl/gl_surface_osmesa.cc
@@ -0,0 +1,61 @@
+// 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.
+
+#include "ui/gfx/gl/gl_surface_osmesa.h"
+#include "base/logging.h"
+#include "ui/gfx/gl/gl_bindings.h"
+
+namespace gfx {
+
+GLSurfaceOSMesa::GLSurfaceOSMesa()
+{
+}
+
+GLSurfaceOSMesa::~GLSurfaceOSMesa() {
+}
+
+void GLSurfaceOSMesa::Resize(const gfx::Size& new_size) {
+  if (new_size == size_)
+    return;
+
+  // Allocate a new back buffer.
+  scoped_array<int32> new_buffer(new int32[new_size.GetArea()]);
+  memset(new_buffer.get(), 0, new_size.GetArea() * sizeof(new_buffer[0]));
+
+  // Copy the current back buffer into the new buffer.
+  int copy_width = std::min(size_.width(), new_size.width());
+  int copy_height = std::min(size_.height(), new_size.height());
+  for (int y = 0; y < copy_height; ++y) {
+    for (int x = 0; x < copy_width; ++x) {
+      new_buffer[y * new_size.width() + x] = buffer_[y * size_.width() + x];
+    }
+  }
+
+  buffer_.reset(new_buffer.release());
+  size_ = new_size;
+}
+
+void GLSurfaceOSMesa::Destroy() {
+  buffer_.reset();
+  size_ = gfx::Size();
+}
+
+bool GLSurfaceOSMesa::IsOffscreen() {
+  return true;
+}
+
+bool GLSurfaceOSMesa::SwapBuffers() {
+  NOTREACHED() << "Should not call SwapBuffers on an GLSurfaceOSMesa.";
+  return false;
+}
+
+gfx::Size GLSurfaceOSMesa::GetSize() {
+  return size_;
+}
+
+void* GLSurfaceOSMesa::GetHandle() {
+  return buffer_.get();
+}
+
+}  // namespace gfx
diff --git a/ui/gfx/gl/gl_surface_osmesa.h b/ui/gfx/gl/gl_surface_osmesa.h
new file mode 100644
index 0000000..742d28a
--- /dev/null
+++ b/ui/gfx/gl/gl_surface_osmesa.h
@@ -0,0 +1,43 @@
+// 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.
+
+#ifndef UI_GFX_GL_GL_SURFACE_OSMESA_H_
+#define UI_GFX_GL_GL_SURFACE_OSMESA_H_
+#pragma once
+
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/gl/gl_surface.h"
+#include "ui/gfx/size.h"
+
+namespace gfx {
+
+// A surface that the Mesa software renderer draws to. This is actually just a
+// buffer in system memory. GetHandle returns a pointer to the buffer. These
+// surfaces can be resized and resizing preserves the contents.
+class GLSurfaceOSMesa : public GLSurface {
+ public:
+  GLSurfaceOSMesa();
+  virtual ~GLSurfaceOSMesa();
+
+  // Resize the back buffer, preserving the old content. Does nothing if the
+  // size is unchanged.
+  void Resize(const gfx::Size& new_size);
+
+  // Implement GLSurface.
+  virtual void Destroy();
+  virtual bool IsOffscreen();
+  virtual bool SwapBuffers();
+  virtual gfx::Size GetSize();
+  virtual void* GetHandle();
+
+ private:
+  gfx::Size size_;
+  scoped_array<int32> buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(GLSurfaceOSMesa);
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_GL_GL_SURFACE_OSMESA_H_