Fix discrepancies in form text selection between PDF and HTML forms.

pdf/pdfium/pdfium_engine.h

Index: pdf/pdfium/pdfium_engine.h
diff --git a/pdf/pdfium/pdfium_engine.h b/pdf/pdfium/pdfium_engine.h
index 5b0e4aa1d84b6858a06922827a6684a20d781a27..4316369ce3993b5d7fbb667bd674243a19948e81 100644
--- a/pdf/pdfium/pdfium_engine.h
+++ b/pdf/pdfium/pdfium_engine.h
@@ -449,6 +449,9 @@ class PDFiumEngine : public PDFEngine,
   // field.
   void SetInFormTextArea(bool in_form_text_area);
 
+  // Sets whether or not left mouse button is currently being held down.
+  void SetMouseHeldDown(bool mouse_held_down);
+
   bool PageIndexInBounds(int index) const;
 
   void ScheduleTouchTimer(const pp::TouchInputEvent& event);
@@ -649,15 +652,26 @@ class PDFiumEngine : public PDFEngine,
   bool defer_page_unload_;
   std::vector<int> deferred_page_unloads_;
 
-  // Used for text selection, but does not include text within form text fields.
+  // Used for text selection, but does not include text within form text areas.
   // There could be more than one range if selection spans more than one page.
   std::vector<PDFiumRange> selection_;
   // True if we're in the middle of text selection.
   bool selecting_;
 
+  // Used for selection of text within form text areas (text fields and combo
+  // box text fields). Represents the currently selected text.
+  std::string selected_form_text_;
+
+  // Used for selection of text within form text areas (text fields and combo
+  // box text fields). Represents the previously selected text.
+  std::string old_selected_form_text_;
+
   // True if focus is in form text field or form combobox text field.
   bool in_form_text_area_;
 
+  // True if left mouse button is currently being held down.
+  bool mouse_held_down_;

[Lei Zhang, 2017/06/29 02:52:46]

Do we need |mouse_held_down_| if we already have |selecting_| on line 659 above?

[drgage, 2017/06/29 17:49:59]

The reason I added |mouse_held_down_| is because the way |selecting_| is
currently being used is for text selection only (i.e. it corresponds to the
|selection_| variable). If you see how it is used in pdfium_engine.cc, it's set
to true in PDFiumEngine::OnSingleClick(), which is only called in
PDFiumEngine::OnMouseDown() in PDFiumPage::TEXT_AREAs. Also, much of what needs
to happen for form text area selection in PDFiumEngine::OnMouseMove() can only
happen if |selecting_| is set to false.

If you think it would make more sense to try to change the way |selecting_| is
being used as opposed to adding another variable, I can look into doing that.

+
   MouseDownState mouse_down_state_;
 
   // Used for searching.