[rAC] Do not re-create bubble window unnecessarily

chrome/browser/ui/cocoa/autofill/autofill_bubble_controller.mm

 // Copyright 2013 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.
 
 #import "chrome/browser/ui/cocoa/autofill/autofill_bubble_controller.h"
 
 #import "chrome/browser/ui/cocoa/autofill/autofill_dialog_constants.h"
 #import "chrome/browser/ui/cocoa/info_bubble_window.h"
 #include "skia/ext/skia_utils_mac.h"
 
 namespace {
 
 // Border inset for error label.
 const CGFloat kLabelInset = 3.0;
 
 const CGFloat kMaxLabelWidth =
     2 * autofill::kFieldWidth + autofill::kHorizontalFieldPadding;
 
 }  // namespace
 
+@interface AutofillBubbleController ()
+
+// Update the current message, keeping arrow location in place.
+- (void)updateMessage:(NSString*)message display:(BOOL)display;
+
+@end
 
 @implementation AutofillBubbleController
 
 - (id)initWithParentWindow:(NSWindow*)parentWindow
                    message:(NSString*)message {
   return [self initWithParentWindow:parentWindow
                             message:message
                               inset:NSMakeSize(kLabelInset, kLabelInset)
                       arrowLocation:info_bubble::kTopCenter];
 }
@@ skipping 13 matching lines @@
                          anchoredAt:NSZeroPoint])) {
     inset_ = inset;
     [self setShouldOpenAsKeyWindow:NO];
     [[self bubble] setArrowLocation:arrowLocation];
     [[self bubble] setAlignment:info_bubble::kAlignArrowToAnchor];
 
     label_.reset([[NSTextField alloc] init]);
     [label_ setEditable:NO];
     [label_ setBordered:NO];
     [label_ setDrawsBackground:NO];
-    [label_ setStringValue:message];
-    NSRect labelFrame = NSMakeRect(inset.width, inset.height, 0, 0);
-    labelFrame.size = [[label_ cell] cellSizeForBounds:
-        NSMakeRect(0, 0, kMaxLabelWidth, CGFLOAT_MAX)];
-    [label_ setFrame:labelFrame];
     [[self bubble] addSubview:label_];
 
-    NSRect windowFrame = [[self window] frame];
-    windowFrame.size = NSMakeSize(
-        NSMaxX([label_ frame]),
-        NSHeight([label_ frame]) + info_bubble::kBubbleArrowHeight);
-    windowFrame = NSInsetRect(windowFrame, -inset.width, -inset.height);
-    [[self window] setFrame:windowFrame display:NO];
+    [self updateMessage:message display:NO];
   }
   return self;
 }
 
 - (CGFloat)maxWidth {
   return kMaxLabelWidth + 2 * inset_.width;
 }
 
+- (void)setMessage:(NSString*)message {
+  if ([[label_ stringValue] isEqualToString:message])
+    return;
+  [self updateMessage:message display:YES];
+}
+
+- (void)updateMessage:(NSString*)message display:(BOOL)display {
+  [label_ setStringValue:message];
+
+  NSRect labelFrame = NSMakeRect(inset_.width, inset_.height, 0, 0);
+  labelFrame.size = [[label_ cell] cellSizeForBounds:
+      NSMakeRect(0, 0, kMaxLabelWidth, CGFLOAT_MAX)];
+  [label_ setFrame:labelFrame];
+
+  // Update window's size, but ensure the origin is maintained so that the arrow
+  // still points at the same location.
+  NSRect windowFrame = [[self window] frame];
+  NSPoint origin = windowFrame.origin;
+  origin.y += NSHeight(windowFrame);
+  windowFrame.size = NSMakeSize(
+      NSMaxX([label_ frame]),
+      NSHeight([label_ frame]) + info_bubble::kBubbleArrowHeight);
+  windowFrame = NSInsetRect(windowFrame, -inset_.width, -inset_.height);
+  origin.y -= NSHeight(windowFrame);
+  windowFrame.origin = origin;
+  [[self window] setFrame:windowFrame display:display];
+}
+
 @end