Only call PDFiumEngine::OnSelectionChanged() when there are changes.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 3272 matching lines @@
     for (auto& old_selection : old_selections_) {
       if (!old_selection.IsEmpty() && new_selection == old_selection) {
         // Rectangle was selected before and after, so no need to invalidate it.
         // Mark the rectangles by setting them to empty.
         new_selection = old_selection = pp::Rect();
         break;
       }
     }
   }
 
+  bool selection_changed = false;
   for (const auto& old_selection : old_selections_) {
-    if (!old_selection.IsEmpty())
+    if (!old_selection.IsEmpty()) {
       engine_->client_->Invalidate(old_selection);
+      selection_changed = true;
+    }
   }
   for (const auto& new_selection : new_selections) {
-    if (!new_selection.IsEmpty())
+    if (!new_selection.IsEmpty()) {
       engine_->client_->Invalidate(new_selection);
+      selection_changed = true;
+    }
   }
-  engine_->OnSelectionChanged();
+  if (selection_changed)
+    engine_->OnSelectionChanged();
 }
 
 void PDFiumEngine::SelectionChangeInvalidator::GetVisibleSelectionsScreenRects(
     std::vector<pp::Rect>* rects) {
   pp::Rect visible_rect = engine_->GetVisibleRect();
   for (auto& range : engine_->selection_) {
     int page_index = range.page_index();
     if (!engine_->IsPageVisible(page_index))
       continue;  // This selection is on a page that's not currently visible.
 
@@ skipping 874 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf