Print preview: Prevent a crash when zooming with the scroll wheel.

chrome/browser/tab_contents/tab_contents_view_gtk.cc

 // Copyright (c) 2011 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 "chrome/browser/tab_contents/tab_contents_view_gtk.h"
 
 #include <gdk/gdk.h>
 #include <gdk/gdkkeysyms.h>
 #include <gtk/gtk.h>
 
@@ skipping 36 matching lines @@
                      TabContents* tab_contents) {
   if (tab_contents->delegate())
     tab_contents->delegate()->ContentsMouseEvent(
         tab_contents, gfx::Point(event->x_root, event->y_root), true);
   return FALSE;
 }
 
 // See tab_contents_view_views.cc for discussion of mouse scroll zooming.
 gboolean OnMouseScroll(GtkWidget* widget, GdkEventScroll* event,
                        TabContents* tab_contents) {
-  if ((event->state & gtk_accelerator_get_default_mod_mask()) ==
+  if ((event->state & gtk_accelerator_get_default_mod_mask()) !=
       GDK_CONTROL_MASK) {
-    if (event->direction == GDK_SCROLL_DOWN) {
-      tab_contents->delegate()->ContentsZoomChange(false);
-      return TRUE;
-    } else if (event->direction == GDK_SCROLL_UP) {
-      tab_contents->delegate()->ContentsZoomChange(true);
-      return TRUE;
-    }
+    return FALSE;
   }
 
-  return FALSE;
+  TabContentsDelegate* delegate = tab_contents->delegate();
+  if (!delegate)
+    return FALSE;
+
+  if (!(event->direction == GDK_SCROLL_DOWN ||
+        event->direction == GDK_SCROLL_UP)) {
+    return FALSE;
+  }
+
+  delegate->ContentsZoomChange(event->direction == GDK_SCROLL_UP);
+  return TRUE;
 }
 
 }  // namespace
 
 TabContentsViewGtk::TabContentsViewGtk(TabContents* tab_contents,
                                        TabContentsViewWrapperGtk* view_wrapper)
     : tab_contents_(tab_contents),
       expanded_(gtk_expanded_container_new()),
       view_wrapper_(view_wrapper),
       overlaid_view_(NULL) {
@@ skipping 335 matching lines @@
   requested_size_ = size;
 
   // We manually tell our RWHV to resize the renderer content.  This avoids
   // spurious resizes from GTK+.
   RenderWidgetHostView* rwhv = tab_contents_->GetRenderWidgetHostView();
   if (rwhv)
     rwhv->SetSize(size);
   if (tab_contents_->interstitial_page())
     tab_contents_->interstitial_page()->SetSize(size);
 }