Fix another discrepancy in text selection between PDF and HTML forms.

pdf/pdfium/pdfium_engine.cc

Index: pdf/pdfium/pdfium_engine.cc
diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index f71ef7ce71f8b2ccb87dc7e2326c1967ee9fe648..37fef3068bc7739a8b2f9acd46cc8ebc2167adbb 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -1653,8 +1653,10 @@ void PDFiumEngine::SetFormSelectedText(FPDF_FORMHANDLE form_handle,
   // selection has changed. If so, set plugin text selection.
   std::string selected_form_text = selected_form_text_;
   selected_form_text_ = base::UTF16ToUTF8(selected_form_text16);
-  if (selected_form_text != selected_form_text_)
+  if (selected_form_text != selected_form_text_) {
+    DCHECK(in_form_text_area_);
     pp::PDF::SetSelectedText(GetPluginInstance(), selected_form_text_.c_str());
+  }
 }
 
 void PDFiumEngine::PrintEnd() {
@@ -1725,7 +1727,8 @@ bool PDFiumEngine::OnMouseDown(const pp::MouseInputEvent& event) {
 
   SetMouseLeftButtonDown(event.GetButton() == PP_INPUTEVENT_MOUSEBUTTON_LEFT);
 
-  SelectionChangeInvalidator selection_invalidator(this);
+  auto selection_invalidator =
+      base::MakeUnique<SelectionChangeInvalidator>(this);
   selection_.clear();
 
   int page_index = -1;
@@ -1755,6 +1758,14 @@ bool PDFiumEngine::OnMouseDown(const pp::MouseInputEvent& event) {
     if (form_type > FPDF_FORMFIELD_UNKNOWN) {  // returns -1 sometimes...
       mouse_down_state_.Set(PDFiumPage::FormTypeToArea(form_type), target);
 
+      // Destroy SelectionChangeInvalidator object before SetInFormTextArea()
+      // changes plugin's focus to be in form text area. This way, regular text
+      // selection can be cleared when a user clicks into a form text area
+      // because the pp::PDF::SetSelectedText() call in
+      // ~SelectionChangeInvalidator() still goes to the Mimehandler
+      // (not the Renderer).
+      selection_invalidator.reset();
+
       bool is_valid_control = (form_type == FPDF_FORMFIELD_TEXTFIELD ||
                                form_type == FPDF_FORMFIELD_COMBOBOX);
 
@@ -3583,6 +3594,7 @@ void PDFiumEngine::GetRegion(const pp::Point& location,
 }
 
 void PDFiumEngine::OnSelectionChanged() {
+  DCHECK(!in_form_text_area_);
   pp::PDF::SetSelectedText(GetPluginInstance(), GetSelectedText().c_str());
 }
 
@@ -3621,6 +3633,13 @@ void PDFiumEngine::SetSelecting(bool selecting) {
 }
 
 void PDFiumEngine::SetInFormTextArea(bool in_form_text_area) {
+  // If focus was previously in form text area, clear form text selection.
+  // Clearing needs to be done before changing focus to ensure the correct
+  // observer is notified of the change in selection. When |in_form_text_area_|
+  // is true, this is the Renderer. After it flips, the MimeHandler is notified.
+  if (in_form_text_area_)
+    pp::PDF::SetSelectedText(GetPluginInstance(), "");
+
   client_->FormTextFieldFocusChange(in_form_text_area);
   in_form_text_area_ = in_form_text_area;
 }