Add comments for struct members that were changed from size_t to uin32_t or uint64_t for IPC safety.

components/autofill/core/common/form_field_data.h

 // 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.
 
 #ifndef COMPONENTS_AUTOFILL_CORE_COMMON_FORM_FIELD_DATA_H_
 #define COMPONENTS_AUTOFILL_CORE_COMMON_FORM_FIELD_DATA_H_
 
 #include <stddef.h>
 
 #include <vector>
@@ skipping 27 matching lines @@
   // Comparison operator exposed for STL map. Uses label, then name to sort.
   bool operator<(const FormFieldData& field) const;
 
   // If you add more, be sure to update the comparison operator, SameFieldAs,
   // serializing functions (in the .cc file) and the constructor.
   base::string16 label;
   base::string16 name;
   base::string16 value;
   std::string form_control_type;
   std::string autocomplete_attribute;
+  // Note: we use uint32_t instead of size_t because this struct is sent over
+  // IPC which could span 32 & 64 bit processes. This is fine since the length
+  // shouldn't exceed UINT32_MAX even on 64 bit builds.
   uint32_t max_length;
   bool is_autofilled;
   bool is_checked;
   bool is_checkable;
   bool is_focusable;
   bool should_autocomplete;
   RoleAttribute role;
   base::i18n::TextDirection text_direction;
 
   // For the HTML snippet |<option value="US">United States</option>|, the
@@ skipping 23 matching lines @@
     EXPECT_EQ(expected.autocomplete_attribute, actual.autocomplete_attribute); \
     EXPECT_EQ(expected.max_length, actual.max_length); \
     EXPECT_EQ(expected.is_autofilled, actual.is_autofilled); \
     EXPECT_EQ(expected.is_checked, actual.is_checked); \
     EXPECT_EQ(expected.is_checkable, actual.is_checkable); \
   } while (0)
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CORE_COMMON_FORM_FIELD_DATA_H_