Use FrameTreeNode ID as frameId in extension APIs

extensions/browser/extension_api_frame_id_map.cc

Index: extensions/browser/extension_api_frame_id_map.cc
diff --git a/extensions/browser/extension_api_frame_id_map.cc b/extensions/browser/extension_api_frame_id_map.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2bfb7a6d87e1c305bcceb986ef1665712f7c749d
--- /dev/null
+++ b/extensions/browser/extension_api_frame_id_map.cc
@@ -0,0 +1,186 @@
+// Copyright 2015 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 "extensions/browser/extension_api_frame_id_map.h"
+
+#include <list>
+#include <map>
+#include <tuple>
+
+#include "base/lazy_instance.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents.h"
+
+namespace extensions {
+
+namespace {
+
+struct RenderFrameIdKey;
+typedef std::list<ExtensionApiFrameIdMap::FrameIdCallback> FrameIdCallbackList;
+typedef std::map<RenderFrameIdKey, ExtensionApiFrameId> FrameIdMap;
+typedef std::map<RenderFrameIdKey, FrameIdCallbackList> CallbackMap;
+
+// Queued callbacks for use on the IO thread. This queue is only used when the
+// frameId needs to be fetched from the UI thread.
+base::LazyInstance<CallbackMap> g_callbacks_map = LAZY_INSTANCE_INITIALIZER;
+
+// This frameId map is only modified on the UI thread and used for two purposes:
+// - On the IO thread, it avoids unnecessary thread hops.
+// - On the UI thread and the IO thread, it ensures that the frameId remains
+//   constant, even after removing a frame.
+// Items are never removed from this map.
+base::LazyInstance<FrameIdMap> g_frame_id_map = LAZY_INSTANCE_INITIALIZER;

[nasko, 2015/12/09 23:06:09]

Why is this map needed and must grow unbound? Why not observe
WebContentsObserver::FrameDeleted and then you know that FTN is gone forever and
the ID will never be used again?

[robwu, 2015/12/10 00:00:51]

Because I think that there is no guarantee that all network requests are
immediately dropped before FrameDeleted, or that there are no webNavigation
events after FrameDeleted (e.g. is there a defined order in RenderFrameDeleted
and FrameDeleted? The former triggers the webNavigation.onErrorOccurred event).

Do you think that it's worthwhile to use a timer or some form of a LRU queue to
bound the map size?

[nasko, 2015/12/17 01:19:48]

There should be no events for webNavigation after a frame is gone.
RenderFrameDeleted should always come before FrameDeleted, so we are ok in that
case.
Why not just update the map? If the frame is gone, the requests/responses will
not be processed by any renderer. In such case, do webRequest extensions need to
know about those, as they will likely have no effect to the user.

+
+// A set of identifiers that uniquely identifies a RenderFrame.
+struct RenderFrameIdKey {
+  RenderFrameIdKey(int process_id, int routing_id)

[nasko, 2015/12/09 23:06:09]

nit: frame_routing_id

[robwu, 2015/12/10 00:00:51]

Done. (everywhere, and also changed process_id to render_process_id).

+      : process_id(process_id), routing_id(routing_id) {}
+
+  // The process ID of the renderer that contains the RenderFrame.
+  int process_id;
+  // The routing ID of the RenderFrame.
+  int routing_id;
+
+  bool operator<(const RenderFrameIdKey& other) const {
+    return std::tie(process_id, routing_id) <
+           std::tie(other.process_id, other.routing_id);
+  }
+};
+
+}  // namespace
+
+ExtensionApiFrameId::ExtensionApiFrameId()
+    : frame_id(kInvalidFrameId), parent_frame_id(kInvalidFrameId) {}
+
+int GetFrameIdFromFrame(content::RenderFrameHost* rfh) {
+  if (!rfh)
+    return ExtensionApiFrameId::kInvalidFrameId;
+  if (rfh->GetParent())
+    return rfh->GetFrameTreeNodeID();
+  return 0;  // Main frame.
+}
+
+void InitializeFromFrame(ExtensionApiFrameId& extension_api_frame_id,
+                         content::RenderFrameHost* rfh) {
+  if (rfh) {

[nasko, 2015/12/09 23:06:09]

We usually use early returns. Example pattern:

if (condition)
  return;

// more work

[robwu, 2015/12/10 00:00:51]

Done.

+    extension_api_frame_id.frame_id = GetFrameIdFromFrame(rfh);
+    extension_api_frame_id.parent_frame_id =
+        GetFrameIdFromFrame(rfh->GetParent());
+  }
+}
+
+const ExtensionApiFrameId& LookupFrameIdOnUI(const RenderFrameIdKey& key) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  FrameIdMap& frame_id_map = g_frame_id_map.Get();
+  FrameIdMap::const_iterator frame_id_iter = frame_id_map.find(key);
+  if (frame_id_iter != frame_id_map.end())
+    return frame_id_iter->second;
+
+  ExtensionApiFrameId& extension_api_frame_id = frame_id_map[key];
+  InitializeFromFrame(
+      extension_api_frame_id,
+      content::RenderFrameHost::FromID(key.process_id, key.routing_id));
+  return extension_api_frame_id;
+}
+
+void GotFrameId(const RenderFrameIdKey& key) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  FrameIdMap& frame_id_map = g_frame_id_map.Get();
+  FrameIdMap::const_iterator frame_id_iter = frame_id_map.find(key);
+  CHECK(frame_id_iter != frame_id_map.end());
+
+  const ExtensionApiFrameId& extension_api_frame_id = frame_id_iter->second;
+  CallbackMap& callbacks_map = g_callbacks_map.Get();
+  FrameIdCallbackList& callbacks = callbacks_map[key];
+  // If GetFrameIdOnIO is called in one of the callbacks, another callback is
+  // appended to the list. So we cannot use a fancy range-based for loop.
+  for (FrameIdCallbackList::iterator it = callbacks.begin();
+       it != callbacks.end(); ++it) {
+    it->Run(extension_api_frame_id);
+  }
+
+  // Remove the callback list. Because the extension frame ID is cached, this
+  // list is never created again for |key|.
+  callbacks_map.erase(key);
+}
+
+void ExtensionApiFrameIdMap::GetFrameIdOnIO(int process_id,
+                                            int routing_id,
+                                            FrameIdCallback callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  const RenderFrameIdKey key(process_id, routing_id);
+  CallbackMap& callbacks_map = g_callbacks_map.Get();
+  CallbackMap::iterator callbacks_iter = callbacks_map.find(key);
+  if (callbacks_iter != callbacks_map.end()) {
+    // There is a pending lookup for the extension frame ID.
+    callbacks_iter->second.push_back(callback);
+    return;
+  }
+
+  FrameIdMap& frame_id_map = g_frame_id_map.Get();
+  FrameIdMap::const_iterator frame_id_iter = frame_id_map.find(key);
+  if (frame_id_iter != frame_id_map.end()) {
+    // The extension frame ID has already been looked up.
+    callback.Run(frame_id_iter->second);
+    return;
+  }
+
+  // The key was seen for the first time, hop to the UI thread to look up the
+  // extension frame ID.
+  callbacks_map[key].push_back(callback);
+  content::BrowserThread::PostTaskAndReply(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(base::IgnoreResult(&LookupFrameIdOnUI), key),
+      base::Bind(&GotFrameId, key));
+}
+
+const ExtensionApiFrameId& ExtensionApiFrameIdMap::GetFrameId(int process_id,
+                                                              int routing_id) {
+  return LookupFrameIdOnUI(RenderFrameIdKey(process_id, routing_id));
+}
+
+const ExtensionApiFrameId& ExtensionApiFrameIdMap::GetFrameId(
+    content::RenderFrameHost* rfh) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  FrameIdMap& frame_id_map = g_frame_id_map.Get();
+  if (!rfh)
+    return frame_id_map[RenderFrameIdKey(-1, -1)];
+
+  const RenderFrameIdKey key(rfh->GetProcess()->GetID(), rfh->GetRoutingID());
+
+  FrameIdMap::const_iterator frame_id_iter = frame_id_map.find(key);
+  if (frame_id_iter != frame_id_map.end())
+    return frame_id_iter->second;
+
+  ExtensionApiFrameId& extension_api_frame_id = frame_id_map[key];
+  InitializeFromFrame(extension_api_frame_id, rfh);
+  return extension_api_frame_id;
+}
+
+content::RenderFrameHost* ExtensionApiFrameIdMap::GetRenderFrameHostById(
+    int frame_id,
+    content::WebContents* web_contents) {
+  // Although it is technically possible to map |frame_id| to a RenderFrameHost
+  // without WebContents, we choose to not do that because in the extension API
+  // frameIds are only guaranteed to be meaningful in combination with a tabId.
+  if (!web_contents)
+    return nullptr;
+
+  if (frame_id == 0)
+    return web_contents->GetMainFrame();
+
+  if (frame_id == -1)
+    return nullptr;
+
+  DCHECK_GE(frame_id, 1);
+  return web_contents->FindFrameByFrameTreeNodeID(frame_id);
+}
+
+}  // namespace extensions