Allow zoom-in as alternative to popup when tapping multiple targets.

content/public/common/renderer_preferences.h

 // 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.
 //
 // A struct for managing browser's settings that apply to the renderer or its
 // webview.  These differ from WebPreferences since they apply to Chromium's
 // glue layer rather than applying to just WebKit.
 //
 // Adding new values to this class probably involves updating
 // common/view_messages.h, browser/browser.cc, etc.
@@ skipping 19 matching lines @@
 
 enum RendererPreferencesSubpixelRenderingEnum {
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_SYSTEM_DEFAULT = 0,
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_NONE,
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_RGB,
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_BGR,
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_VRGB,
   RENDERER_PREFERENCES_SUBPIXEL_RENDERING_VBGR,
 };
 
+enum DidTapMultipleTargetsStrategy {
+  MULTITARGET_ZOOM = 0,

[jam, 2013/07/30 16:12:40]

nit: use content api convention for enums value names, i.e.

enum TapMultipleTargetsStrategy {
TAP_MULTIPLE_TARGETS_STRATEGY_ZOOM,
TAP_MULTIPLE_TARGETS_STRATEGY_POPUP,
};

+  MULTITARGET_POPUP,
+
+  MULTITARGET_MAX = MULTITARGET_POPUP,
+};
+
 struct CONTENT_EXPORT RendererPreferences {
   RendererPreferences();
   ~RendererPreferences();
 
   // Whether the renderer's current browser context accept drops from the OS
   // that result in navigations away from the current page.
   bool can_accept_load_drops;
 
   // Whether text should be antialiased.
   // Currently only used by Linux.
@@ skipping 69 matching lines @@
   // Sunspider. We need to find an efficient way to report changes to frame
   // names to the browser process. See http://crbug.com/169110 for more
   // information.
   bool report_frame_name_changes;
 
   // Controls deacceleration of touchpad-initiated flings.
   std::vector<float> touchpad_fling_profile;
 
   // Controls deacceleration of touchscreen-initiated flings.
   std::vector<float> touchscreen_fling_profile;
+
+  // How to handle a tap gesture touching multiple targets
+  DidTapMultipleTargetsStrategy did_tap_multiple_targets_strategy;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_COMMON_RENDERER_PREFERENCES_H_