Allow Offline MHTML save operations to succeed even with missing frames.

content/browser/download/mhtml_generation_manager.cc

Index: content/browser/download/mhtml_generation_manager.cc
diff --git a/content/browser/download/mhtml_generation_manager.cc b/content/browser/download/mhtml_generation_manager.cc
index e2ad052318e6a2cf5a9a92ea00880c98fbb1452f..0884890e8e57b06ad92b725d1cc4d810ae0f7f85 100644
--- a/content/browser/download/mhtml_generation_manager.cc
+++ b/content/browser/download/mhtml_generation_manager.cc
@@ -204,19 +204,25 @@ MhtmlSaveStatus MHTMLGenerationManager::Job::SendToNextRenderFrame() {
   DCHECK(browser_file_.IsValid());
   DCHECK(!pending_frame_tree_node_ids_.empty());
 
+  int frame_tree_node_id = pending_frame_tree_node_ids_.front();
+  pending_frame_tree_node_ids_.pop();
+  FrameTreeNode* ftn = FrameTreeNode::GloballyFindByID(frame_tree_node_id);
+  if (!ftn) {  // A previously existing frame went away.
+    if (!params_.ignore_missing_frames)
+      return MhtmlSaveStatus::FRAME_NO_LONGER_EXISTS;
+    else if (pending_frame_tree_node_ids_.empty())
+      return MhtmlSaveStatus::SUCCESS;
+    else
+      return SendToNextRenderFrame();
+  }
+
   FrameMsg_SerializeAsMHTML_Params ipc_params;
   ipc_params.job_id = job_id_;
   ipc_params.mhtml_boundary_marker = mhtml_boundary_marker_;
   ipc_params.mhtml_binary_encoding = params_.use_binary_encoding;
   ipc_params.mhtml_cache_control_policy = params_.cache_control_policy;
-
-  int frame_tree_node_id = pending_frame_tree_node_ids_.front();
-  pending_frame_tree_node_ids_.pop();
   ipc_params.is_last_frame = pending_frame_tree_node_ids_.empty();
 
-  FrameTreeNode* ftn = FrameTreeNode::GloballyFindByID(frame_tree_node_id);
-  if (!ftn)  // The contents went away.
-    return MhtmlSaveStatus::FRAME_NO_LONGER_EXISTS;
   RenderFrameHost* rfh = ftn->current_frame_host();
 
   // Get notified if the target of the IPC message dies between responding.