Support dragging texts out of webview/Chrome.

content/browser/web_contents/web_contents_view_android.cc

Index: content/browser/web_contents/web_contents_view_android.cc
diff --git a/content/browser/web_contents/web_contents_view_android.cc b/content/browser/web_contents/web_contents_view_android.cc
index 8c326e0c0ca3be8771203bc8b9de5664003857de..0118b3a14de60e79f48fdc7b4d5dd8e5c86ad681 100644
--- a/content/browser/web_contents/web_contents_view_android.cc
+++ b/content/browser/web_contents/web_contents_view_android.cc
@@ -194,7 +194,10 @@ void WebContentsViewAndroid::StartDragging(
     const gfx::ImageSkia& image,
     const gfx::Vector2d& image_offset,
     const DragEventSourceInfo& event_info) {
-  NOTIMPLEMENTED();
+  if (drop_data.text.is_null())
+    return;
+  base::string16 dragged_text = drop_data.text.string();
+  content_view_core_->StartDragging(dragged_text, image);
 }
 
 void WebContentsViewAndroid::UpdateDragCursor(blink::WebDragOperation op) {
@@ -205,14 +208,20 @@ void WebContentsViewAndroid::OnDragEntered(
     const std::vector<DropData::Metadata>& metadata,
     const gfx::Point& location,
     const gfx::Point& screen_location) {
+  blink::WebDragOperationsMask allowed_ops =
+      static_cast<blink::WebDragOperationsMask>(blink::WebDragOperationCopy |
+                                                blink::WebDragOperationMove);

[dcheng, 2016/07/08 06:30:30]

Out of curiosity, why did we change this from Copy to Copy+Move?

[hush (inactive), 2016/07/08 18:23:24]

The move operation is to support dragging texts within the same chrome tab or
the same webview. Android TextView does this too: when you drag within the same
view, it's gonna be a move, otherwise a copy.

So if I don't allow move here, WebViewImpl::dragTargetDrop will just early out
(because blink wants to move the text but wasn't allowed to do so, as a result,
m_dragOperation in WebViewImpl is set to WebDragOperationNone)
See here
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/web/WebViewImp...

   web_contents_->GetRenderViewHost()->DragTargetDragEnterWithMetaData(
-      metadata, location, screen_location, blink::WebDragOperationCopy, 0);
+      metadata, location, screen_location, allowed_ops, 0);
 }
 
 void WebContentsViewAndroid::OnDragUpdated(const gfx::Point& location,
                                            const gfx::Point& screen_location) {
+  blink::WebDragOperationsMask allowed_ops =
+      static_cast<blink::WebDragOperationsMask>(blink::WebDragOperationCopy |
+                                                blink::WebDragOperationMove);
   web_contents_->GetRenderViewHost()->DragTargetDragOver(
-      location, screen_location, blink::WebDragOperationCopy, 0);
+      location, screen_location, allowed_ops, 0);
 }
 
 void WebContentsViewAndroid::OnDragExited() {
@@ -227,6 +236,10 @@ void WebContentsViewAndroid::OnPerformDrop(DropData* drop_data,
                                                      screen_location, 0);
 }
 
+void WebContentsViewAndroid::OnDragEnded() {
+  web_contents_->GetRenderViewHost()->DragSourceSystemDragEnded();
+}
+
 void WebContentsViewAndroid::GotFocus() {
   // This is only used in the views FocusManager stuff but it bleeds through
   // all subclasses. http://crbug.com/21875