Fix help text size calculation for password gen bubble on Mac.

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

 // Copyright 2014 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/password_generation_popup_view_cocoa.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 146 matching lines @@
   CGFloat width =
       autofill::kPopupBorderThickness +
       controller_->kHorizontalPadding +
       [[keyIcon_ image] size].width +
       controller_->kHorizontalPadding +
       std::max(passwordSize.width, passwordTitleSize.width) +
       controller_->kHorizontalPadding +
       autofill::kPopupBorderThickness;
 
   width = std::max(width, (CGFloat)controller_->GetMinimumWidth());
+  CGFloat contentWidth = width - (2 * controller_->kHorizontalPadding);
 
   CGFloat height =
       autofill::kPopupBorderThickness +
       controller_->kHelpVerticalPadding +
-      [self helpSizeForPopupWidth:width].height +
+      [self helpSizeForPopupWidth:contentWidth].height +
       controller_->kHelpVerticalPadding +
       autofill::kPopupBorderThickness;
 
   if (controller_->display_password())
     height += controller_->kPopupPasswordSectionHeight;
 
   return NSMakeSize(width, height);
 }
 
 - (void)updateBoundsAndRedrawPopup {
@@ skipping 147 matching lines @@
 
 - (NSFont*)boldFont {
   return [NSFont boldSystemFontOfSize:[NSFont smallSystemFontSize]];
 }
 
 - (NSFont*)textFont {
   return [NSFont systemFontOfSize:[NSFont smallSystemFontSize]];
 }
 
 @end