Reapply "Let Layout::GetSupportedScaleFactorFromScale() return only supported ScaleFactor."

ui/base/layout.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 "ui/base/layout.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
@@ skipping 92 matching lines @@
 #elif defined(OS_WIN)
   if (UseTouchOptimizedUI())
     return LAYOUT_TOUCH;
   return LAYOUT_DESKTOP;
 #else
   return LAYOUT_DESKTOP;
 #endif
 }
 
 ScaleFactor GetScaleFactorFromScale(float scale) {
-  size_t closest_match = 0;
+  ScaleFactor closest_match = SCALE_FACTOR_100P;
   float smallest_diff =  std::numeric_limits<float>::max();
-  for (size_t i = 0; i < kScaleFactorScalesLength; ++i) {
-    float diff = std::abs(kScaleFactorScales[i] - scale);
+  const std::vector<ScaleFactor>& supported =
+      GetSupportedScaleFactorsInternal();
+  for (size_t i = 0; i < supported.size(); ++i) {
+    ScaleFactor scale_factor = supported[i];
+    float diff = std::abs(kScaleFactorScales[scale_factor] - scale);
     if (diff < smallest_diff) {
-      closest_match = i;
+      closest_match = scale_factor;
       smallest_diff = diff;
     }
   }
-  return static_cast<ui::ScaleFactor>(closest_match);
+  return closest_match;
 }
 
 float GetScaleFactorScale(ScaleFactor scale_factor) {
   return kScaleFactorScales[scale_factor];
 }
 
 std::vector<ScaleFactor> GetSupportedScaleFactors() {
   return GetSupportedScaleFactorsInternal();
 }
 
@@ skipping 24 matching lines @@
   return GetScaleFactorFromScale(
       root_window->compositor()->device_scale_factor());
 #else
   NOTIMPLEMENTED();
   return SCALE_FACTOR_NONE;
 #endif
 }
 #endif  // !defined(OS_MACOSX)
 
 }  // namespace ui