Add an interface to gather text surrounding the selection.

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index 0fdc058b01df1913bdd2fd047833cf83185792e2..672389aa1490d17ea288ee0c127d91192601e27a 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -37,6 +37,7 @@
 #include "content/browser/screen_orientation/screen_orientation_dispatcher_host.h"
 #include "content/browser/ssl/ssl_host_state.h"
 #include "content/browser/web_contents/web_contents_view_android.h"
+#include "content/common/frame_messages.h"
 #include "content/common/input/web_input_event_traits.h"
 #include "content/common/input_messages.h"
 #include "content/common/view_messages.h"
@@ -1538,6 +1539,17 @@ void ContentViewCoreImpl::SetAccessibilityEnabledInternal(bool enabled) {
   }
 }
 
+void ContentViewCoreImpl::OnTextSurroundingSelectionResponse(
+    const base::string16& content,
+    int start_offset,
+    int end_offset) {
+  if (text_surroundings_callback_.is_null())
+    return;
+  text_surroundings_callback_.Run(content, start_offset, end_offset);
+  // Re-initialize to the is_null value.

[jdduke (slow), 2014/06/18 20:32:53]

In the comments what if we instead say "The callback should be run but once, as
it's tied to the request." making it clear why we're resetting the callback.

[donnd, 2014/06/18 21:55:27]

Done.

+  text_surroundings_callback_ = TextSurroundingSelectionCallback();
+}
+
 void ContentViewCoreImpl::SendOrientationChangeEventInternal() {
   RenderWidgetHostViewAndroid* rwhv = GetRenderWidgetHostViewAndroid();
   if (rwhv)
@@ -1604,6 +1616,18 @@ void ContentViewCoreImpl::SetBackgroundOpaque(JNIEnv* env, jobject jobj,
     GetRenderWidgetHostViewAndroid()->SetBackgroundOpaque(opaque);
 }
 
+void ContentViewCoreImpl::RequestTextSurroundingSelection(
+    int max_length, const TextSurroundingSelectionCallback& callback) {
+  RenderFrameHost* focused_frame = web_contents_->GetFocusedFrame();
+  if (!focused_frame)
+    return;
+  if (!text_surroundings_callback_.is_null())

[jdduke (slow), 2014/06/18 20:32:53]

I'm not sure if we should be DCHECK'ing, here, but a comment saying "Only one
outstanding request is allowed at any given time." might be appropriate.

I've been thinking about this some more, it's possible the renderer crashes
while the request is made, in which case we never get the response.  In that
case, the callback will always be non-null, preventing subsequent queries. Not
sure what the best solution is there, perhaps we store the callback in
RenderWidgetHostViewAndroid, and it gets cleared when we change the
ContentViewCore or the renderer crashes.  Maybe Ted has some better ideas about
managing lifetimes here.

[donnd, 2014/06/18 21:55:27]

Glad you caught this possibility!  I changed the return when non-null into a
DCHECK because I think it would be pretty bad if we blocked subsequent queries.
I also put in a comment as you suggested, and I've also added a TODO to capture
this issue.  

I'll ask Ted when passing on for him to review.

+    return;
+  text_surroundings_callback_ = callback;
+  focused_frame->Send(new FrameMsg_TextSurroundingSelectionRequest(
+      focused_frame->GetRoutingID(), max_length));
+}
+
 void ContentViewCoreImpl::OnSmartClipDataExtracted(
     const base::string16& result) {
   JNIEnv* env = AttachCurrentThread();