Floor rather than round the top border thickness.

chrome/browser/ui/views/frame/glass_browser_frame_view.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 "chrome/browser/ui/views/frame/glass_browser_frame_view.h"
 
 #include <utility>
 
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
@@ skipping 308 matching lines @@
 int GlassBrowserFrameView::FrameBorderThickness() const {
   return (frame()->IsMaximized() || frame()->IsFullscreen()) ?
       0 : display::win::GetSystemMetricsInDIP(SM_CXSIZEFRAME);
 }
 
 int GlassBrowserFrameView::FrameTopBorderThickness(bool restored) const {
   // Distinct from FrameBorderThickness() because Windows gives maximized
   // windows an offscreen CYSIZEFRAME-thick region around the edges. The
   // left/right/bottom edges don't worry about this because we cancel them out
   // in BrowserDesktopWindowTreeHostWin::GetClientAreaInsets() so the offscreen
-  // area is non-client as far as Windows is concerned. However because we want
-  // to push away the top part of the glass's gradient in Win7 we set the top
-  // client inset to 0. Thus we must compensate here to avoid having UI elements
-  // drift off the top of the screen.
-  return (frame()->IsFullscreen() && !restored) ?
-      0 : display::win::GetSystemMetricsInDIP(SM_CYSIZEFRAME);
+  // area is non-client as far as Windows is concerned. However we can't do this
+  // with the top inset because otherwise Windows will give us a standard
+  // titlebar. Thus we must compensate here to avoid having UI elements drift
+  // off the top of the screen.
+  if (frame()->IsFullscreen() && !restored)
+    return 0;
+  // Mouse and touch locations are floored but GetSystemMetricsInDIP is rounded,
+  // so we need to floor instead or else the difference will cause the hittest
+  // to fail when it ought to succeed.
+  return std::floor(GetSystemMetrics(SM_CYSIZEFRAME) /
+                    display::win::GetDPIScale());
 }
 
 int GlassBrowserFrameView::TopAreaHeight(bool restored) const {
   if (frame()->IsFullscreen() && !restored)
     return 0;
 
   const int top = FrameTopBorderThickness(restored);
   // The tab top inset is equal to the height of any shadow region above the
   // tabs, plus a 1 px top stroke.  In maximized mode, we want to push the
   // shadow region off the top of the screen but leave the top stroke.
@@ skipping 323 matching lines @@
   static bool initialized = false;
   if (!initialized) {
     for (int i = 0; i < kThrobberIconCount; ++i) {
       throbber_icons_[i] =
           ui::LoadThemeIconFromResourcesDataDLL(IDI_THROBBER_01 + i);
       DCHECK(throbber_icons_[i]);
     }
     initialized = true;
   }
 }