Don't crash when using IME on an input field with a CSS-specified font.

content/common/mac/attributed_string_coder.mm

 // 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 "content/common/mac/attributed_string_coder.h"
 
 #include <AppKit/AppKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 82 matching lines @@
 }
 
 AttributedStringCoder::FontAttribute::FontAttribute()
     : font_descriptor_(),
       effective_range_() {
 }
 
 AttributedStringCoder::FontAttribute::~FontAttribute() {
 }
 
-NSDictionary* AttributedStringCoder::FontAttribute::ToAttributesDictionary(
-    void) const {
+NSDictionary*
+AttributedStringCoder::FontAttribute::ToAttributesDictionary() const {
   DCHECK(ShouldEncode());
   NSFont* font = font_descriptor_.ToNSFont();
+  if (!font)
+    return [NSDictionary dictionary];
   return [NSDictionary dictionaryWithObject:font forKey:NSFontAttributeName];
 }
 
 bool AttributedStringCoder::FontAttribute::ShouldEncode() const {
   return !font_descriptor_.font_name.empty();
 }
 
 }  // namespace mac
 
 // IPC ParamTraits specialization //////////////////////////////////////////////
@@ skipping 45 matching lines @@
     *p = AttributedStringCoder::FontAttribute(font, range);
   }
   return success;
 }
 
 void ParamTraits<AttributedStringCoder::FontAttribute>::Log(
     const param_type& p, std::string* l) {
 }
 
 }  // namespace IPC