[Mac RTL] Draw the drop arrow in the correct location when mirrored.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

Index: chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm b/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
index ac56c5b6aa1f02730602ec168f632d7cc3b122f2..760d031e0026a4e9f1a08e8c80bfb1e71bb98879 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
@@ -2206,13 +2206,21 @@ NSRect FlipRectInView(NSView* view, NSRect rect) {
     DCHECK(disposition == WindowOpenDisposition::NEW_FOREGROUND_TAB);
     NSInteger lastIndex = [tabArray_ count] - 1;
     NSRect overRect = [[[tabArray_ objectAtIndex:lastIndex] view] frame];
-    arrowPos.x = overRect.origin.x + overRect.size.width - kTabOverlap / 2.0;
+    if (cocoa_l10n_util::ShouldDoExperimentalRTLLayout()) {
+      arrowPos.x = NSMinX(overRect) + kTabOverlap / 2.0;
+    } else {
+      arrowPos.x = NSMaxX(overRect) - kTabOverlap / 2.0;
+    }
   } else {
     NSRect overRect = [[[tabArray_ objectAtIndex:index] view] frame];
     switch (disposition) {
       case WindowOpenDisposition::NEW_FOREGROUND_TAB:
-        // Insert tab (to the left of the given tab).
-        arrowPos.x = overRect.origin.x + kTabOverlap / 2.0;
+        // Insert tab (before the given tab).
+        if (cocoa_l10n_util::ShouldDoExperimentalRTLLayout()) {
+          arrowPos.x = NSMaxX(overRect) - kTabOverlap / 2.0;
+        } else {
+          arrowPos.x = NSMinX(overRect) + kTabOverlap / 2.0;
+        }
         break;
       case WindowOpenDisposition::CURRENT_TAB:
         // Overwrite the given tab.