[Cronet] Add CrNet.setUserAgent method on iOS.

ios/crnet/CrNet.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.
 
 #import <Foundation/Foundation.h>
 
 // A block, that takes a request, and returns YES if the request should
 // be handled.
 typedef BOOL(^RequestFilterBlock)(NSURLRequest *request);
 
@@ skipping 18 matching lines @@
 // effect before |install| is called.
 + (void)setQuicEnabled:(BOOL)quicEnabled;
 
 // Sets whether SDCH should be supported by CrNet. This method only has any
 // effect before |install| is called. The |filename| argument is used to specify
 // which file should be used for SDCH persistence metadata. If |filename| is
 // nil, persistence is not enabled. The default is for SDCH to be disabled.
 + (void)setSDCHEnabled:(BOOL)sdchEnabled
          withPrefStore:(NSString *)filename;
 
-// |userAgent| is expected to be of the form Product/Version.
-// Example: Foo/3.0.0.0
+// Set partial UserAgent. This function is a deprecated shortcut for:
+//    [CrNet setUserAgent:userAgent partial:YES];
+// See the documentation for |setUserAgent| for details about the |userAgent|
+// argument.
+// This method only has any effect before |install| is called.
++ (void)setPartialUserAgent:(NSString *)userAgent;
+
+// |userAgent| is expected to be the user agent value sent to remote.
+// If |partial| is set to YES, then actual user agent value is based on device
+// model, OS version, and |userAgent| argument. For example "Foo/3.0.0.0" is
+// sent as "Mozilla/5.0 (iPhone; CPU iPhone OS 9_3 like Mac OS X)
+// AppleWebKit/601.1 (KHTML, like Gecko) Foo/3.0.0.0 Mobile/15G31
+// Safari/601.1.46".
+// If partial is set to NO, then |userAgent| value is complete value sent to
+// the remote. For Example: "Foo/3.0.0.0" is sent as "Foo/3.0.0.0".
 //
 // This method only has any effect before |install| is called.
-+ (void)setPartialUserAgent:(NSString *)userAgent;
++ (void)setUserAgent:(NSString*)userAgent partial:(bool)partial;
 
 // Set the block used to determine whether or not CrNet should handle the
 // request. If this is not set, CrNet will handle all requests.
 // Must not be called while requests are in progress. This method can be called
 // either before or after |install|.
 + (void)setRequestFilterBlock:(RequestFilterBlock)block;
 
 // Installs CrNet. Once installed, CrNet intercepts and handles all
 // NSURLConnection and NSURLRequests issued by the app, including UIWebView page
 // loads. It is recommended to call this method on the application main thread.
@@ skipping 58 matching lines @@
 
 // Returns the full user-agent that the stack uses.
 // This is the exact string servers will see.
 + (NSString *)userAgent;
 
 // Clears CrNet's http cache. The supplied callback, if not nil, is run on an
 // unspecified thread.
 + (void)clearCacheWithCompletionCallback:(ClearCacheCallback)completionBlock;
 
 @end