[iOS] Upstream some stability code

ios/chrome/browser/crash_report/crash_report_multi_parameter.h

+// 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.
+
+#ifndef IOS_CHROME_BROWSER_CRASH_REPORT_CRASH_REPORT_MULTI_PARAMETER_H_
+#define IOS_CHROME_BROWSER_CRASH_REPORT_CRASH_REPORT_MULTI_PARAMETER_H_
+
+#include <Foundation/Foundation.h>
+
+// CrashReportMultiParameter keeps state of multiple report values that will be
+// grouped in a single breakpad element to save limited number of breakpad
+// values.
+@interface CrashReportMultiParameter : NSObject
+// Init with the breakpad parameter key.
+- (instancetype)initWithKey:(NSString*)key NS_DESIGNATED_INITIALIZER;
+
+- (instancetype)init NS_UNAVAILABLE;
+
+// Adds or updates an element in the dictionary of the breakpad report. Value
+// are stored in the instance so every time you call this function, the whole
+// JSON dictionary is regenerated. The total size of the serialized dictionary
+// bmust e under 256 bytes due to Breakpad limitation. Setting a value to 0 will
+// not remove the key. Use [removeValue:key] instead.
+- (void)setValue:(NSString*)key withValue:(int)value;
+
+// Removes the key element from the dictionary. Note that this is different from
+// setting the parameter to 0 or false.
+- (void)removeValue:(NSString*)key;
+
+// Increases the key element by one.
+- (void)incrementValue:(NSString*)key;
+
+// Decreases the key element by one. If the element is 0, the element is removed
+// from the dictionary.
+- (void)decrementValue:(NSString*)key;
+@end
+
+#endif  // IOS_CHROME_BROWSER_CRASH_REPORT_CRASH_REPORT_MULTI_PARAMETER_H_