[Cocoa] DevTools: align devtools splitter to integer pixels to avoid half-pixel artifacts on HiDPI.

chrome/browser/ui/cocoa/dev_tools_controller.mm

Index: chrome/browser/ui/cocoa/dev_tools_controller.mm
diff --git a/chrome/browser/ui/cocoa/dev_tools_controller.mm b/chrome/browser/ui/cocoa/dev_tools_controller.mm
index 4c90907a8edc9d6ea6ed352f53dc27d45811dc28..6fb204d2f429373a7766476ec089c9d31985be52 100644
--- a/chrome/browser/ui/cocoa/dev_tools_controller.mm
+++ b/chrome/browser/ui/cocoa/dev_tools_controller.mm
@@ -217,6 +217,12 @@ using content::WebContents;
   }
 }
 
+- (CGFloat)splitView:(NSSplitView *)splitView
+    constrainSplitPosition:(CGFloat)proposedPosition
+               ofSubviewAt:(NSInteger)dividerIndex {
+  return round(proposedPosition);
+}
+
 -(void)splitViewWillResizeSubviews:(NSNotification *)notification {
   [[splitView_ window] disableScreenUpdatesUntilFlush];
 }