Fix race conditions in window snapshot code.

content/renderer/render_view_impl.cc

 // Copyright (c) 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 "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/debug/alias.h"
 #include "base/debug/trace_event.h"
 #include "base/files/file_path.h"
 #include "base/i18n/char_iterator.h"
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/metrics/histogram.h"
 #include "base/path_service.h"
 #include "base/process/kill.h"
+#include "base/process/process.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "content/child/appcache/appcache_dispatcher.h"
 #include "content/child/appcache/web_application_cache_host_impl.h"
 #include "content/child/child_thread.h"
@@ skipping 151 matching lines @@
 #include "third_party/WebKit/public/web/WebSecurityPolicy.h"
 #include "third_party/WebKit/public/web/WebSerializedScriptValue.h"
 #include "third_party/WebKit/public/web/WebSettings.h"
 #include "third_party/WebKit/public/web/WebStorageQuotaCallbacks.h"
 #include "third_party/WebKit/public/web/WebUserGestureIndicator.h"
 #include "third_party/WebKit/public/web/WebUserMediaClient.h"
 #include "third_party/WebKit/public/web/WebView.h"
 #include "third_party/WebKit/public/web/WebWindowFeatures.h"
 #include "third_party/WebKit/public/web/default/WebRenderTheme.h"
 #include "ui/base/ui_base_switches_util.h"
+#include "ui/events/latency_info.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
 #include "ui/shell_dialogs/selected_file_info.h"
 #include "v8/include/v8.h"
 #include "webkit/child/weburlresponse_extradata_impl.h"
 
 #if defined(OS_ANDROID)
@@ skipping 2023 matching lines @@
   if (RenderThreadImpl::current())  // Will be NULL during unit tests.
     RenderThreadImpl::current()->DoNotNotifyWebKitOfModalLoop();
 
   message->EnableMessagePumping();  // Runs a nested message loop.
   return Send(message);
 }
 
 void RenderViewImpl::GetWindowSnapshot(const WindowSnapshotCallback& callback) {
   int id = next_snapshot_id_++;
   pending_snapshots_.insert(std::make_pair(id, callback));
-  Send(new ViewHostMsg_GetWindowSnapshot(routing_id_, id));
+  ui::LatencyInfo latency_info;
+  latency_info.AddLatencyNumber(ui::WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT,
+                                GetLatencyComponentId(),
+                                id);
+  if (RenderWidgetCompositor* rwc = compositor()) {
+    rwc->SetLatencyInfo(latency_info);
+  } else {
+    latency_info_.MergeWith(latency_info);
+  }
+  ScheduleCompositeWithForcedRedraw();
 }
 
 void RenderViewImpl::OnWindowSnapshotCompleted(const int snapshot_id,
     const gfx::Size& size, const std::vector<unsigned char>& png) {
-  PendingSnapshotMap::iterator it = pending_snapshots_.find(snapshot_id);
-  DCHECK(it != pending_snapshots_.end());
-  it->second.Run(size, png);
-  pending_snapshots_.erase(it);
+

[bajones, 2013/09/26 22:27:23]

@jbauman: Sorry I missed this on my last pass. This code scans through all
pending snapshot requests and fires of the completed callback for any with an id
<= the completed snapshot. This should prevent any requests from becoming
orphaned by sharing a swap. Please let me know if you have concerns about this
approach! 

+  // Any pending snapshots with a lower ID than the one received are considered
+  // to be implicitly complete, and returned the same snapshot data.
+  PendingSnapshotMap::iterator it = pending_snapshots_.begin();
+  while(it != pending_snapshots_.end()) {
+      if (it->first <= snapshot_id) {
+        it->second.Run(size, png);
+        pending_snapshots_.erase(it++);
+      } else {
+        ++it;
+      }
+  }
 }
 
 // WebKit::WebViewClient ------------------------------------------------------
 
 WebView* RenderViewImpl::createView(
     WebFrame* creator,
     const WebURLRequest& request,
     const WebWindowFeatures& features,
     const WebString& frame_name,
     WebNavigationPolicy policy) {
@@ skipping 455 matching lines @@
   }
 }
 
 gfx::RectF RenderViewImpl::ClientRectToPhysicalWindowRect(
     const gfx::RectF& rect) const {
   gfx::RectF window_rect = rect;
   window_rect.Scale(device_scale_factor_ * webview()->pageScaleFactor());
   return window_rect;
 }
 
+int64 RenderViewImpl::GetLatencyComponentId() {
+  // Note: this must match the logic in RenderWidgetHostImpl.
+  return GetRoutingID() | (static_cast<int64>(
+      RenderThreadImpl::current()->renderer_process_id()) << 32);
+}
+
 void RenderViewImpl::StartNavStateSyncTimerIfNecessary() {
   // No need to update state if no page has committed yet.
   if (page_id_ == -1)
     return;
 
   int delay;
   if (send_content_state_immediately_)
     delay = 0;
   else if (is_hidden())
     delay = kDelaySecondsForContentStateSyncHidden;
@@ skipping 3770 matching lines @@
   for (size_t i = 0; i < icon_urls.size(); i++) {
     WebURL url = icon_urls[i].iconURL();
     if (!url.isEmpty())
       urls.push_back(FaviconURL(url,
                                 ToFaviconType(icon_urls[i].iconType())));
   }
   SendUpdateFaviconURL(urls);
 }
 
 }  // namespace content