Fix double lock of texture resource in software renderer

cc/output/software_renderer.cc

 // Copyright 2012 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 "cc/output/software_renderer.h"
 
 #include "base/trace_event/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
@@ skipping 142 matching lines @@
   DCHECK(!output_surface_->HasExternalStencilTest());
   current_framebuffer_lock_ = nullptr;
   current_framebuffer_canvas_.clear();
   current_canvas_ = root_canvas_;
 }
 
 bool SoftwareRenderer::BindFramebufferToTexture(
     DrawingFrame* frame,
     const ScopedResource* texture,
     const gfx::Rect& target_rect) {
+  current_framebuffer_lock_ = nullptr;
   current_framebuffer_lock_ = make_scoped_ptr(
       new ResourceProvider::ScopedWriteLockSoftware(
           resource_provider_, texture->id()));
   current_framebuffer_canvas_ =
       skia::AdoptRef(new SkCanvas(current_framebuffer_lock_->sk_bitmap()));
   current_canvas_ = current_framebuffer_canvas_.get();
   InitializeViewport(frame,
                      target_rect,
                      gfx::Rect(target_rect.size()),
                      target_rect.size());
@@ skipping 434 matching lines @@
 }
 
 void SoftwareRenderer::DidChangeVisibility() {
   if (visible())
     EnsureBackbuffer();
   else
     DiscardBackbuffer();
 }
 
 }  // namespace cc