[Android] Fix XWALK unable to support download behavior

Several bugs reported that Xwalk not able to support "download" attribute from anchor since XWALK4
Changes in this commit
1) Implement onDownloadStart method in XWalkContentsClientBridge to call download listener method
2) Ignore render_frame_id which is set to MSG_ROUTING_NONE from content for download request
3) In runtime_download_manager_deledate, return the suggested path to content
4) In runtime_resource_dispatcher_host_delegate_android, don't cancel request, because content will use it later on to futher operation(rename, trunk..etc)

BUG=https://crosswalk-project.org/jira/browse/XWALK-1079

Author: js0701

runtime/android/core_internal/src/org/xwalk/core/internal/XWalkContentsClientBridge.java

@@ -373,12 +373,16 @@ public void onDownloadStart(String url,
                                 String contentDisposition,
                                 String mimeType,
                                 long contentLength) {
+       if (mDownloadListener != null) {
+           mDownloadListener.onDownloadStart(url, userAgent, contentDisposition,
+                                             mimeType, contentLength);
+       }
     }
 
     @Override
     public boolean onCreateWindow(boolean isDialog, boolean isUserGesture) {
         if (isDialog) return false;
-        
+
         XWalkUIClientInternal.InitiateByInternal initiator =
                 XWalkUIClientInternal.InitiateByInternal.BY_JAVASCRIPT;
         if (isUserGesture) {

runtime/browser/android/xwalk_contents_io_thread_client_impl.cc

@@ -89,8 +89,21 @@ void RfhToIoThreadClientMap::Set(pair<int, int> rfh_id,
 bool RfhToIoThreadClientMap::Get(
     pair<int, int> rfh_id, IoThreadClientData* client) {
   base::AutoLock lock(map_lock_);
-  RenderFrameHostToIoThreadClientType::iterator iterator =
-      rfh_to_io_thread_client_.find(rfh_id);
+  RenderFrameHostToIoThreadClientType::iterator iterator;
+
+  if (rfh_id.second != MSG_ROUTING_NONE) {
+    iterator = rfh_to_io_thread_client_.find(rfh_id);
+  } else {
+    // Content use render_frame_id= MSG_ROUTING_NONE for download request
+    // So just find the matched process_id
+    iterator = rfh_to_io_thread_client_.begin();
+    while (iterator != rfh_to_io_thread_client_.end()) {
+      if (iterator->first.first == rfh_id.first)
+        break;
+      iterator++;
+    }
+  }
+
   if (iterator == rfh_to_io_thread_client_.end())
     return false;
 

runtime/browser/runtime_download_manager_delegate.cc

@@ -164,7 +164,7 @@ void RuntimeDownloadManagerDelegate::ChooseDownloadPath(
   if (GetSaveFileName(&save_as))
     result = base::FilePath(std::wstring(save_as.lpstrFile));
 #else
-  NOTIMPLEMENTED();
+  result = suggested_path;
 #endif
 
   callback.Run(result, content::DownloadItem::TARGET_DISPOSITION_PROMPT,

runtime/browser/runtime_resource_dispatcher_host_delegate_android.cc

@@ -259,8 +259,6 @@ void RuntimeResourceDispatcherHostDelegateAndroid::DownloadStarting(
     response_headers->GetMimeType(&mime_type);
   }
 
-  request->Cancel();
-
   const content::ResourceRequestInfo* request_info =
       content::ResourceRequestInfo::ForRequest(request);