Adds support for POST request with bodies on WKWebView.

ios/web/web_state/js/crw_js_post_request_loader.mm

Index: ios/web/web_state/js/crw_js_post_request_loader.mm
diff --git a/ios/web/web_state/js/crw_js_post_request_loader.mm b/ios/web/web_state/js/crw_js_post_request_loader.mm
new file mode 100644
index 0000000000000000000000000000000000000000..735e76ab8e0a1014eac3a28d813697c53dea5dec
--- /dev/null
+++ b/ios/web/web_state/js/crw_js_post_request_loader.mm
@@ -0,0 +1,168 @@
+// Copyright 2015 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 "ios/web/web_state/js/crw_js_post_request_loader.h"
+
+#include "base/json/string_escape.h"
+#include "base/mac/objc_property_releaser.h"

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

s/include/import

[stkhapugin, 2015/12/03 15:43:02]

Done.

+#include "base/strings/sys_string_conversions.h"
+#import "ios/web/web_state/js/page_script_util.h"
+#import "ios/web/web_state/ui/crw_wk_script_message_router.h"
+
+namespace {
+
+// Escapes characters and encloses given string in quotes for use in JavaScript.
+NSString* EscapeAndQuoteStringForJavaScript(NSString* unescapedString) {
+  std::string string = base::SysNSStringToUTF8(unescapedString);
+  return base::SysUTF8ToNSString(base::GetQuotedJSONString(string));
+}
+
+NSString* const kErrorHandlerName = @"POSTErrorHandler";

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

These need comments

[stkhapugin, 2015/12/03 15:43:02]

Done.

+NSString* const kSuccessHandlerName = @"POSTSuccess";
+
+}  // namespace
+
+@interface CRWJSPOSTRequestLoader () {
+  base::mac::ObjCPropertyReleaser _propertyReleaser_CRWJSPOSTRequestLoader;
+}
+
+// JavaScript used to execute POST requests. Lazily instantiated.
+@property(nonatomic, retain) NSString* requestScript;
+
+// Handler for UIApplicationDidReceiveMemoryWarningNotification.
+- (void)handleMemoryWarning;
+
+// Forms a JavaScript method call to |requestScript| that executes given
+// |request|.
+- (NSString*)stringToExecutePOSTRequest:(NSURLRequest*)request;

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

s/stringToExecutePOSTRequest:/scriptToExecutePOSTRequest:

[stkhapugin, 2015/12/03 15:43:02]

Done.

+
+// Converts a dictionary of HTTP request headers to a JavaScript object.
+- (NSString*)stringForJavaScriptFromRequestHeaders:(NSDictionary*)headers;

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

s/stringForJavaScriptFromRequestHeaders:/JSONForJavaScriptFromRequestHeaders:

[stkhapugin, 2015/12/03 15:43:01]

Done.

+
+@end
+
+@implementation CRWJSPOSTRequestLoader
+@synthesize requestScript = _requestScript;
+
+- (void)dealloc {
+  [[NSNotificationCenter defaultCenter] removeObserver:self];
+  [super dealloc];
+}
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    _propertyReleaser_CRWJSPOSTRequestLoader.Init(
+        self, [CRWJSPOSTRequestLoader class]);
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(handleMemoryWarning)
+               name:UIApplicationDidReceiveMemoryWarningNotification
+             object:nil];
+  }
+  return self;
+}
+
+- (NSString*)requestScript {
+  if (!_requestScript) {
+    _requestScript = [web::GetPageScript(@"post_request") retain];

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

s/retain/copy

Strings should be copied.
https://google.github.io/styleguide/objcguide.xml?showone=Use_Root_Frameworks...

[stkhapugin, 2015/12/03 15:43:02]

Done.

+  }
+  return _requestScript;
+}
+
+- (void)loadPOSTRequest:(NSURLRequest*)request
+              inWebView:(WKWebView*)webView
+          messageRouter:(CRWWKScriptMessageRouter*)messageRouter
+             errorBlock:(void (^)(NSError*))errorBlock
+           successBlock:(void (^)())successBlock {
+  DCHECK([request.HTTPMethod isEqualToString:@"POST"]);
+  DCHECK(webView);
+  DCHECK(messageRouter);
+  DCHECK(errorBlock);
+
+  // Install error handling and success routers.
+  [messageRouter setScriptMessageHandler:^(WKScriptMessage* message) {
+    // Cleaning up script handlers.
+    // This needs to be done on next runloop because this block gets deallocated
+    // during its execution otherwise.

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

Which block is deallocated? one which is passed to |setScriptMessageHandler:| or
|successBlock|?

[stkhapugin, 2015/12/03 15:43:02]

The message handler block (the one where this comment is) is only retained by
the dictionary in message router. Once you removeScriptHandlerForName:webView:,
this block gets deallocated while being executed. 

[Eugene But (OOO till 7-30), 2015/12/03 16:51:42]

Thank you for explanation. I think it will be cleaner if you change
ScriptMessageRouter as follows:

- (void)tryRemoveScriptMessageHandlerForName:(NSString*)messageName
                                     webView:(WKWebView*)webView {
  NSMapTable* webViewToHandlerMap = [_handlers objectForKey:messageName];
  id handler = [webViewToHandlerMap objectForKey:webView];
  if (!handler)
    return;
  // Extend the lifetime of |handler| so removeScriptMessageHandlerForName: can
be called from
  // inside of |handler|.
  [[handler retain] autorelease];
  if (webViewToHandlerMap.count == 1) {
    [_handlers removeObjectForKey:messageName];
    [_userContentController removeScriptMessageHandlerForName:messageName];
  } else {
    [webViewToHandlerMap removeObjectForKey:webView];
  }
}

[stkhapugin, 2015/12/03 17:51:02]

Done.

+    dispatch_async(dispatch_get_main_queue(), ^{
+      [messageRouter removeScriptMessageHandlerForName:kErrorHandlerName
+                                               webView:webView];
+      [messageRouter removeScriptMessageHandlerForName:kSuccessHandlerName
+                                               webView:webView];
+      if (successBlock) {
+        successBlock();
+      }
+    });
+  }
+                                    name:kSuccessHandlerName
+                                 webView:webView];
+
+  [messageRouter setScriptMessageHandler:^(WKScriptMessage* message) {
+    NSNumber* statusCode = message.body;
+    NSError* error = [NSError errorWithDomain:@"http"

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

Please add a constant for error domain and put it to the header. Also it should
be something less generic that @http"

[stkhapugin, 2015/12/03 15:43:02]

Since the only error that can happen here is HTTP, should I use NSURLErrorDomain
or something like that to get the default handling for HTTP errors? 

[Eugene But (OOO till 7-30), 2015/12/03 16:51:42]

NSURLErrorDomain is used by System libraries, so we should not use it. Since
WebController does not actually use that NSError, I think the easiest way would
be replacing NSError with |BOOL success|. What do you think?

[stkhapugin, 2015/12/03 17:51:02]

I agree that it's not necessary to emit an NSError here, but how should a
non-200 status be handled then?

[Eugene But (OOO till 7-30), 2015/12/03 18:13:21]

Oh, I'm sorry, I'm blind. WC actually uses that NSError. I guess using
NSURLErrorDomain is fine (not ideal, but fine). 

[stkhapugin, 2015/12/04 16:28:09]

Done.

+                                         code:[statusCode integerValue]

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

Optional NIT: s/[statusCode integerValue]/statusCode.integerValue

[stkhapugin, 2015/12/03 15:43:02]

Done.

+                                     userInfo:nil];
+    // Cleaning up script handlers.
+    // This needs to be done on next runloop because this block gets deallocated
+    // during its execution otherwise.
+    dispatch_async(dispatch_get_main_queue(), ^{
+      [messageRouter removeScriptMessageHandlerForName:kErrorHandlerName
+                                               webView:webView];
+      [messageRouter removeScriptMessageHandlerForName:kSuccessHandlerName
+                                               webView:webView];
+      errorBlock(error);
+    });
+  }
+                                    name:kErrorHandlerName
+                                 webView:webView];
+
+  NSString* js = [self requestScript];

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

Optional NIT: s/[self requestScript]/self.requestScript

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

NIT: Please drop this variable and just inline the call. If you don't want to do
that then s/js/JS

[stkhapugin, 2015/12/03 15:43:02]

Done.

[stkhapugin, 2015/12/03 15:43:02]

Done.

+  NSString* HTML =
+      [NSString stringWithFormat:@"<html><script>%@%@</script></html>", js,
+                                 [self stringToExecutePOSTRequest:request]];
+  [webView loadHTMLString:HTML baseURL:request.URL];
+}
+
+#pragma mark - Private methods.
+
+- (void)handleMemoryWarning {
+  // Request script can be recreated from file at any moment.
+  self.requestScript = nil;
+}
+
+- (NSString*)stringToExecutePOSTRequest:(NSURLRequest*)request {
+  NSDictionary* headers = [request allHTTPHeaderFields];
+  NSString* headerString = [self stringForJavaScriptFromRequestHeaders:headers];
+  NSString* URLString = [[request URL] absoluteString];
+  NSString* contentType = headers[@"Content-Type"];
+  NSString* base64Data = [[request HTTPBody] base64EncodedStringWithOptions:0];
+
+  return [NSString
+      stringWithFormat:@"__crPostRequestHack.runPostRequest(%@, %@, %@, %@)",

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

s/Hack/Workaround :)

[stkhapugin, 2015/12/03 15:43:02]

Done.

+                       EscapeAndQuoteStringForJavaScript(URLString),
+                       headerString,
+                       EscapeAndQuoteStringForJavaScript(base64Data),
+                       EscapeAndQuoteStringForJavaScript(contentType)];
+}
+
+- (NSString*)stringForJavaScriptFromRequestHeaders:(NSDictionary*)headers {
+  NSData* headerData = nil;
+  if (headers) {

[Eugene But (OOO till 7-30), 2015/12/02 17:06:15]

Optional NIT: I would restructure this:

if (headers) {
  NSData* headerData =
      [NSJSONSerialization dataWithJSONObject:headers options:0 error:nil];
  if (headerData) {
    return [[[NSString alloc] initWithData:headerData
encoding:NSUTF8StringEncoding] autorelease];
  }
}
return @"{}";

[stkhapugin, 2015/12/03 15:43:02]

Done.

+    headerData =
+        [NSJSONSerialization dataWithJSONObject:headers options:0 error:nil];
+  }
+  NSString* headerString = @"{}";
+  if (headerData) {
+    // This string is properly escaped by NSJSONSerialization. It needs to have
+    // no quotes since JavaScripts takes this parameter as an
+    // Object<string, string>.
+    headerString =
+        [[[NSString alloc] initWithData:headerData
+                               encoding:NSUTF8StringEncoding] autorelease];
+  }
+  return headerString;
+}
+
+@end