Specify a default display UI scale to reset the zoom to

ash/display/display_manager.cc

Index: ash/display/display_manager.cc
diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 50aabb503ef9db6108ef075ae3b3c4ee3f7b1c7e..2262abf4cd3033846bf392347e8d1fe4bc530f0d 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -129,6 +129,20 @@ scoped_refptr<display::ManagedDisplayMode> GetDisplayModeForUIScale(
   return *iter;
 }
 
+scoped_refptr<display::ManagedDisplayMode> GetDefaultDisplayMode(
+    const display::ManagedDisplayInfo& info) {
+  const auto& modes = info.display_modes();
+  auto iter =
+      std::find_if(modes.begin(), modes.end(),
+                   [](const scoped_refptr<display::ManagedDisplayMode>& mode) {
+                     return mode->is_default();
+                   });
+
+  if (iter == modes.end())
+    return scoped_refptr<display::ManagedDisplayMode>();
+  return *iter;
+}
+
 }  // namespace
 
 using std::string;
@@ -1110,6 +1124,16 @@ bool DisplayManager::SetDisplayUIScale(int64_t id, float ui_scale) {
   return SetDisplayMode(id, mode);
 }
 
+bool DisplayManager::ResetDisplayToDefaultMode(int64_t display_id) {
+  if (!IsActiveDisplayId(display_id))

[oshima, 2016/10/19 21:04:06]

Check internal display as well.

[afakhry, 2016/10/24 20:21:46]

Done.

+    return false;
+
+  const display::ManagedDisplayInfo& info = GetDisplayInfo(display_id);
+  scoped_refptr<display::ManagedDisplayMode> mode = GetDefaultDisplayMode(info);
+
+  return mode ? SetDisplayMode(display_id, mode) : false;
+}
+
 void DisplayManager::ResetInternalDisplayZoom() {
   if (IsInUnifiedMode()) {
     const display::ManagedDisplayInfo& display_info =
@@ -1123,7 +1147,7 @@ void DisplayManager::ResetInternalDisplayZoom() {
         });
     SetDisplayMode(kUnifiedDisplayId, *iter);
   } else {
-    SetDisplayUIScale(GetDisplayIdForUIScaling(), 1.0f);
+    ResetDisplayToDefaultMode(GetDisplayIdForUIScaling());
   }
 }