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..b117acb0e6fab55b0baabe34a08710366fe4771b 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -114,16 +114,15 @@ gfx::Size GetMaxNativeSize(const display::ManagedDisplayInfo& info) {
   return size;
 }
 
-scoped_refptr<display::ManagedDisplayMode> GetDisplayModeForUIScale(
-    const display::ManagedDisplayInfo& info,
-    float ui_scale) {
-  const display::ManagedDisplayInfo::ManagedDisplayModeList& modes =
-      info.display_modes();
-  auto iter = std::find_if(
-      modes.begin(), modes.end(),
-      [ui_scale](const scoped_refptr<display::ManagedDisplayMode>& mode) {
-        return mode->ui_scale() == ui_scale;
-      });
+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;
@@ -1097,17 +1096,14 @@ bool DisplayManager::ZoomInternalDisplay(bool up) {
   return mode ? SetDisplayMode(display_id, mode) : false;
 }
 
-bool DisplayManager::SetDisplayUIScale(int64_t id, float ui_scale) {
-  if (!IsActiveDisplayId(id) || !display::Display::IsInternalDisplayId(id)) {
+bool DisplayManager::ResetDisplayToDefaultMode(int64_t id) {
+  if (!IsActiveDisplayId(id) || !display::Display::IsInternalDisplayId(id))
     return false;
-  }
+
   const display::ManagedDisplayInfo& info = GetDisplayInfo(id);
+  scoped_refptr<display::ManagedDisplayMode> mode = GetDefaultDisplayMode(info);
 
-  scoped_refptr<display::ManagedDisplayMode> mode =
-      GetDisplayModeForUIScale(info, ui_scale);
-  if (!mode)
-    return false;
-  return SetDisplayMode(id, mode);
+  return mode ? SetDisplayMode(id, mode) : false;
 }
 
 void DisplayManager::ResetInternalDisplayZoom() {
@@ -1123,7 +1119,7 @@ void DisplayManager::ResetInternalDisplayZoom() {
         });
     SetDisplayMode(kUnifiedDisplayId, *iter);
   } else {
-    SetDisplayUIScale(GetDisplayIdForUIScaling(), 1.0f);
+    ResetDisplayToDefaultMode(GetDisplayIdForUIScaling());
   }
 }