Allow changing DownloadTask's mime type during the download.

Response's MIME type can change during the download and DownloadTask
should support the change. This will allow to report
DOWNLOAD_PASS_KIT_WRONG_MIME_TYPE_FAILURE metric for PassKit downloads.

Bug: 787943
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I137f9aa4ff966c140a9a6cb5b03dc026062bc0b7
Reviewed-on: https://chromium-review.googlesource.com/786265Reviewed-by: Gregory Chatzinoff <gchatz@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519521}

ios/web/download/download_task_impl.mm

@@ -8,6 +8,7 @@
 #import <WebKit/WebKit.h>
 
 #import "base/mac/bind_objc_block.h"
+#include "base/strings/sys_string_conversions.h"
 #import "ios/web/net/cookies/wk_cookie_util.h"
 #include "ios/web/public/browser_state.h"
 #import "ios/web/public/download/download_task_observer.h"
@@ -248,6 +249,8 @@ NSURLSession* DownloadTaskImpl::CreateSession(NSString* identifier) {
         error_code_ = GetNetErrorCodeFromNSError(error);
         percent_complete_ = GetTaskPercentComplete(task);
         total_bytes_ = task.countOfBytesExpectedToReceive;
+        if (task.response.MIMEType)
+          mime_type_ = base::SysNSStringToUTF8(task.response.MIMEType);
 
         if (task.state != NSURLSessionTaskStateCompleted) {
           OnDownloadUpdated();

ios/web/download/download_task_impl_unittest.mm

@@ -460,6 +460,32 @@ TEST_F(DownloadTaskImplTest, FileDeletion) {
   EXPECT_CALL(task_delegate_, OnTaskDestroyed(task_.get()));
 }
 
+// Tests changing MIME type during the download.
+TEST_F(DownloadTaskImplTest, MimeTypeChange) {
+  EXPECT_CALL(task_observer_, OnDownloadUpdated(task_.get()));
+  CRWFakeNSURLSessionTask* session_task = Start();
+  ASSERT_TRUE(session_task);
+  testing::Mock::VerifyAndClearExpectations(&task_observer_);
+
+  // Download has finished with a different MIME type.
+  ASSERT_EQ(kMimeType, task_->GetMimeType());
+  EXPECT_CALL(task_observer_, OnDownloadUpdated(task_.get()));
+  const char kOtherMimeType[] = "application/foo";
+  session_task.response =
+      [[NSURLResponse alloc] initWithURL:[NSURL URLWithString:@(kUrl)]
+                                MIMEType:@(kOtherMimeType)
+                   expectedContentLength:0
+                        textEncodingName:nil];
+  SimulateDownloadCompletion(session_task);
+  testing::Mock::VerifyAndClearExpectations(&task_observer_);
+  ASSERT_TRUE(WaitUntilConditionOrTimeout(kWaitForDownloadTimeout, ^{
+    return task_->IsDone();
+  }));
+  EXPECT_EQ(kOtherMimeType, task_->GetMimeType());
+
+  EXPECT_CALL(task_delegate_, OnTaskDestroyed(task_.get()));
+}
+
 // Tests that destructing DownloadTaskImpl calls -[NSURLSessionDataTask cancel]
 // and OnTaskDestroyed().
 TEST_F(DownloadTaskImplTest, DownloadTaskDestruction) {

ios/web/test/fakes/crw_fake_nsurl_session_task.h

@@ -18,6 +18,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic) int64_t countOfBytesReceived;
 @property(nonatomic) int64_t countOfBytesExpectedToReceive;
 @property(nonatomic) NSURLSessionTaskState state;
+@property(nonatomic, nullable, copy) NSURLResponse* response;
 
 - (nullable instancetype)initWithURL:(NSURL*)URL NS_DESIGNATED_INITIALIZER;
 - (nullable instancetype)init NS_UNAVAILABLE;

ios/web/test/fakes/crw_fake_nsurl_session_task.mm

@@ -21,6 +21,7 @@
 @synthesize state = _state;
 @synthesize originalRequest = _originalRequest;
 @synthesize currentRequest = _currentRequest;
+@synthesize response = _response;
 
 - (instancetype)initWithURL:(NSURL*)URL {
   if ((self = [super init])) {