Adds selection expansion support for Contextual Search.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index f9e0d27b6cda63713529379fcef821f22f0c7aa2..622e2ed9abfa90cae7dddf50dbc9d59ff0c2ff68 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1009,6 +1009,8 @@ bool RenderFrameImpl::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(InputMsg_Delete, OnDelete)
     IPC_MESSAGE_HANDLER(InputMsg_SelectAll, OnSelectAll)
     IPC_MESSAGE_HANDLER(InputMsg_SelectRange, OnSelectRange)
+    IPC_MESSAGE_HANDLER(InputMsg_AdjustSelectionByCharacterOffset,
+                        OnAdjustSelectionByCharacterOffset)
     IPC_MESSAGE_HANDLER(InputMsg_Unselect, OnUnselect)
     IPC_MESSAGE_HANDLER(InputMsg_MoveRangeSelectionExtent,
                         OnMoveRangeSelectionExtent)
@@ -1325,6 +1327,28 @@ void RenderFrameImpl::OnSelectRange(const gfx::Point& base,
   frame_->selectRange(base, extent);
 }
 
+void RenderFrameImpl::OnAdjustSelectionByCharacterOffset(int start_adjust,
+                                                         int end_adjust) {
+  size_t start, length;
+  if (!GetRenderWidget()->webwidget()->caretOrSelectionRange(
+      &start, &length)) {
+    return;
+  }
+
+  // Sanity checks to disallow empty and out of range selections.
+  if (start_adjust - end_adjust < length || -start_adjust > start) {
+    return;
+  }
+
+  // A negative adjust amount moves the selection towards the beginning of
+  // the document, a positive amount moves the selection towards the end of
+  // the document.
+  start += start_adjust;
+  length += end_adjust - start_adjust;
+
+  frame_->selectRange(WebRange::fromDocumentRange(frame_, start, length));
+}
+
 void RenderFrameImpl::OnUnselect() {
   base::AutoReset<bool> handling_select_range(&handling_select_range_, true);
   frame_->executeCommand(WebString::fromUTF8("Unselect"), GetFocusedElement());