Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/intercepting_resource_handler_unittest.cc

+// Copyright 2016 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.
+
+#include "content/browser/loader/intercepting_resource_handler.h"
+
+#include <stdint.h>
+
+#include <memory>
+
+#include "base/files/file_path.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "content/public/browser/resource_controller.h"
+#include "content/public/browser/resource_request_info.h"
+#include "content/public/common/resource_response.h"
+#include "content/public/common/webplugininfo.h"
+#include "content/public/test/test_browser_thread_bundle.h"
+#include "content/public/test/test_utils.h"
+#include "net/base/net_errors.h"
+#include "net/url_request/url_request_context.h"
+#include "net/url_request/url_request_status.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+namespace content {
+
+namespace {
+
+class TestResourceHandler : public ResourceHandler {
+ public:
+  // A test version of a ResourceHandler. |request_status| and
+  // |final_bytes_read| will be updated when the response is complete with the
+  // final status of the request received by the handler, and the total bytes
+  // the handler saw.
+  explicit TestResourceHandler(net::URLRequestStatus* request_status,
+                               size_t* final_bytes_read)
+      : TestResourceHandler(request_status,
+                            final_bytes_read,
+                            true /* on_response_started_result */,
+                            true /* on_will_read_result */,
+                            true /* on_read_completed_result */) {}
+
+  // This constructor allows to specify return values for OnResponseStarted,
+  // OnWillRead and OnReadCompleted.
+  TestResourceHandler(net::URLRequestStatus* request_status,
+                      size_t* final_bytes_read,
+                      bool on_response_started_result,
+                      bool on_will_read_result,
+                      bool on_read_completed_result)
+      : ResourceHandler(nullptr),
+        buffer_(new net::IOBuffer(2048)),
+        request_status_(request_status),
+        final_bytes_read_(final_bytes_read),
+        on_response_started_result_(on_response_started_result),
+        on_will_read_result_(on_will_read_result),
+        on_read_completed_result_(on_read_completed_result),
+        bytes_read_(0),
+        is_completed_(false) {
+    memset(buffer_->data(), '\0', 2048);
+  }
+
+  ~TestResourceHandler() override {}
+
+  void SetController(ResourceController* controller) override {}
+
+  bool OnRequestRedirected(const net::RedirectInfo& redirect_info,
+                           ResourceResponse* response,
+                           bool* defer) override {
+    NOTREACHED();
+    return false;
+  }
+
+  bool OnResponseStarted(ResourceResponse* response, bool* defer) override {
+    EXPECT_FALSE(is_completed_);
+    return on_response_started_result_;
+  }
+
+  bool OnWillStart(const GURL& url, bool* defer) override {
+    EXPECT_FALSE(is_completed_);
+    return true;
+  }
+
+  bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                  int* buf_size,
+                  int min_size) override {
+    EXPECT_FALSE(is_completed_);
+    *buf = buffer_;
+    *buf_size = 2048;
+    memset(buffer_->data(), '\0', 2048);
+    return on_will_read_result_;
+  }
+
+  bool OnReadCompleted(int bytes_read, bool* defer) override {
+    EXPECT_FALSE(is_completed_);
+    EXPECT_LT(bytes_read, 2048);
+    bytes_read_ += bytes_read;
+    return on_read_completed_result_;
+  }
+
+  void OnResponseCompleted(const net::URLRequestStatus& status,
+                           const std::string& security_info,
+                           bool* defer) override {
+    EXPECT_FALSE(is_completed_);
+    is_completed_ = true;
+    *request_status_ = status;
+    *final_bytes_read_ = bytes_read_;
+  }
+
+  void OnDataDownloaded(int bytes_downloaded) override { NOTREACHED(); }
+
+  scoped_refptr<net::IOBuffer> buffer() const { return buffer_; }
+
+  size_t bytes_read() const { return bytes_read_; }
+
+ private:
+  scoped_refptr<net::IOBuffer> buffer_;
+  net::URLRequestStatus* request_status_;
+  size_t* final_bytes_read_;
+  bool on_response_started_result_;
+  bool on_will_read_result_;
+  bool on_read_completed_result_;
+  size_t bytes_read_;
+  bool is_completed_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestResourceHandler);
+};
+
+class InterceptingResourceHandlerTest : public testing::Test {
+ public:
+  InterceptingResourceHandlerTest() {}
+
+ private:
+  TestBrowserThreadBundle thread_bundle_;
+};
+
+// Tests that the handler behaves properly when it doesn't have to use an
+// alternate next handler.
+TEST_F(InterceptingResourceHandlerTest, NoSwitching) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read));
+  TestResourceHandler* old_test_handler = old_handler.get();
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const std::string kData = "The data";
+  EXPECT_NE(kData, std::string(old_test_handler->buffer()->data()));
+
+  ASSERT_EQ(read_buffer.get(), old_test_handler->buffer());
+  ASSERT_GT(static_cast<size_t>(buf_size), kData.length());
+  memcpy(read_buffer->data(), kData.c_str(), kData.length());
+
+  // The response is received. The handler should not change.
+  EXPECT_TRUE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+
+  // The read is replayed by the MimeSniffingResourceHandler. The data should
+  // have been received by the old intercepting_handler.
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData, std::string(old_test_handler->buffer()->data()));
+
+  // Make sure another read behave as expected.
+  buf_size = 0;
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+  ASSERT_EQ(read_buffer.get(), old_test_handler->buffer());
+
+  const std::string kData2 = "Data 2";
+  EXPECT_NE(kData, std::string(old_test_handler->buffer()->data()));
+  ASSERT_GT(static_cast<size_t>(buf_size), kData2.length());
+  memcpy(read_buffer->data(), kData2.c_str(), kData2.length());
+
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData2.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData2, std::string(old_test_handler->buffer()->data()));
+  EXPECT_EQ(kData.length() + kData2.length(), old_test_handler->bytes_read());
+}
+
+// Tests that the data received is transmitted to the newly created
+// ResourceHandler.
+TEST_F(InterceptingResourceHandlerTest, HandlerSwitchNoPayload) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read));
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const std::string kData = "The data";
+  ASSERT_EQ(read_buffer.get(), old_buffer.get());
+  ASSERT_GT(static_cast<size_t>(buf_size), kData.length());
+  memcpy(read_buffer->data(), kData.c_str(), kData.length());
+
+  // Simulate the MimeSniffingResourceHandler asking the
+  // InterceptingResourceHandler to switch to a new handler.
+  net::URLRequestStatus new_handler_status;
+  size_t new_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> new_handler_scoped(
+      new TestResourceHandler(&new_handler_status,
+                              &new_handler_final_bytes_read));
+  TestResourceHandler* new_test_handler = new_handler_scoped.get();
+  intercepting_handler->UseNewHandler(std::move(new_handler_scoped),
+                                      std::string());
+
+  // The response is received. The new ResourceHandler should be used handle
+  // the download.
+  EXPECT_TRUE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+
+  EXPECT_FALSE(old_handler_status.is_success());
+  EXPECT_EQ(net::ERR_ABORTED, old_handler_status.error());
+  EXPECT_EQ(0ul, old_handler_final_bytes_read);
+
+  // It should not have received the download data yet.
+  EXPECT_NE(kData, std::string(new_test_handler->buffer()->data()));
+
+  // The read is replayed by the MimeSniffingResourceHandler. The data should
+  // have been received by the new handler.
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData, std::string(new_test_handler->buffer()->data()));
+
+  // Make sure another read behaves as expected.
+  buf_size = 0;
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+  ASSERT_EQ(read_buffer.get(), new_test_handler->buffer());
+  ASSERT_GT(static_cast<size_t>(buf_size), kData.length());
+
+  const std::string kData2 = "Data 2";
+  EXPECT_NE(kData2, std::string(new_test_handler->buffer()->data()));
+  memcpy(read_buffer->data(), kData2.c_str(), kData2.length());
+
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData2.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData2, std::string(new_test_handler->buffer()->data()));
+  EXPECT_EQ(kData.length() + kData2.length(), new_test_handler->bytes_read());
+}
+
+// Tests that the data received is transmitted to the newly created
+// ResourceHandler and the specified payload to the old ResourceHandler.
+TEST_F(InterceptingResourceHandlerTest, HandlerSwitchWithPayload) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler_scoped(
+      new TestResourceHandler(&old_handler_status,
+                              &old_handler_final_bytes_read));
+  TestResourceHandler* old_handler = old_handler_scoped.get();
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler_scoped),
+                                      request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const std::string kData = "The data";
+  ASSERT_EQ(read_buffer.get(), old_buffer.get());
+  ASSERT_GT(static_cast<size_t>(buf_size), kData.length());
+  memcpy(read_buffer->data(), kData.c_str(), kData.length());
+
+  // Simulate the MimeSniffingResourceHandler asking the
+  // InterceptingResourceHandler to switch to a new handler.
+  const std::string kPayload = "The payload";
+  net::URLRequestStatus new_handler_status;
+  size_t new_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> new_handler_scoped(
+      new TestResourceHandler(&new_handler_status,
+                              &new_handler_final_bytes_read));
+  TestResourceHandler* new_test_handler = new_handler_scoped.get();
+  intercepting_handler->UseNewHandler(std::move(new_handler_scoped), kPayload);
+
+  // The old handler should not have received the payload yet.
+  ASSERT_FALSE(old_handler->bytes_read());
+  EXPECT_NE(kPayload, std::string(old_buffer->data()));
+
+  // The response is received. The new ResourceHandler should be used to handle
+  // the download.
+  EXPECT_TRUE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+
+  // The old handler should have received the payload.
+  ASSERT_TRUE(old_handler_final_bytes_read == kPayload.size());
+  EXPECT_EQ(kPayload, std::string(old_buffer->data()));
+
+  EXPECT_TRUE(old_handler_status.is_success());
+  EXPECT_EQ(net::OK, old_handler_status.error());
+
+  // It should not have received the download data yet.
+  EXPECT_NE(kData, std::string(new_test_handler->buffer()->data()));
+
+  // The read is replayed by the MimeSniffingResourceHandler. The data should
+  // have been received by the new handler.
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData, std::string(new_test_handler->buffer()->data()));
+
+  // Make sure another read behave as expected.
+  buf_size = 0;
+  const std::string kData2 = "Data 2";
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+  ASSERT_EQ(read_buffer.get(), new_test_handler->buffer());
+  ASSERT_GT(static_cast<size_t>(buf_size), kData.length());
+
+  EXPECT_NE(kData2, std::string(new_test_handler->buffer()->data()));
+  memcpy(read_buffer->data(), kData2.c_str(), kData2.length());
+
+  EXPECT_TRUE(intercepting_handler->OnReadCompleted(kData2.length(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(kData2, std::string(new_test_handler->buffer()->data()));
+  EXPECT_EQ(kData.length() + kData2.length(), new_test_handler->bytes_read());
+}
+
+// Tests that the handler behaves properly if the old handler fails will read.
+TEST_F(InterceptingResourceHandlerTest, OldHandlerFailsWillRead) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read,
+      true,    // on_response_started
+      false,   // on_will_read
+      true));  // on_read_completed
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data. The old
+  // handler should tell the caller to fail.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_FALSE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+}
+
+// Tests that the handler behaves properly if the new handler fails response
+// started.
+TEST_F(InterceptingResourceHandlerTest, NewHandlerFailsResponseStarted) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read));
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const char kData[] = "The data";
+  ASSERT_EQ(read_buffer.get(), old_buffer.get());
+  ASSERT_GT(static_cast<size_t>(buf_size), sizeof(kData));
+  memcpy(read_buffer->data(), kData, sizeof(kData));
+
+  // Simulate the MimeSniffingResourceHandler asking the
+  // InterceptingResourceHandler to switch to a new handler.
+  net::URLRequestStatus new_handler_status;
+  size_t new_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> new_handler(new TestResourceHandler(
+      &new_handler_status, &new_handler_final_bytes_read,
+      false,   // on_response_started
+      true,    // on_will_read
+      true));  // on_read_completed
+  intercepting_handler->UseNewHandler(std::move(new_handler), std::string());
+
+  // The response is received. The new ResourceHandler should tell us to fail.
+  EXPECT_FALSE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+}
+
+// Tests that the handler behaves properly if the new handler fails will read.
+TEST_F(InterceptingResourceHandlerTest, NewHandlerFailsWillRead) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read));
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const char kData[] = "The data";
+  ASSERT_EQ(read_buffer.get(), old_buffer.get());
+  ASSERT_GT(static_cast<size_t>(buf_size), sizeof(kData));
+  memcpy(read_buffer->data(), kData, sizeof(kData));
+
+  // Simulate the MimeSniffingResourceHandler asking the
+  // InterceptingResourceHandler to switch to a new handler.
+  net::URLRequestStatus new_handler_status;
+  size_t new_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> new_handler(new TestResourceHandler(
+      &new_handler_status, &new_handler_final_bytes_read,
+      true,    // on_response_started
+      false,   // on_will_read
+      true));  // on_read_completed
+  intercepting_handler->UseNewHandler(std::move(new_handler), std::string());
+
+  // The response is received. The new handler should not have been asked to
+  // read yet.
+  EXPECT_TRUE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(net::URLRequestStatus::CANCELED, old_handler_status.status());
+  EXPECT_EQ(net::ERR_ABORTED, old_handler_status.error());
+
+  // The read is replayed by the MimeSniffingResourceHandler. The new
+  // handler should tell the caller to fail.
+  EXPECT_FALSE(intercepting_handler->OnReadCompleted(sizeof(kData), &defer));
+  EXPECT_FALSE(defer);
+}
+
+// Tests that the handler behaves properly if the new handler fails read
+// completed.
+TEST_F(InterceptingResourceHandlerTest, NewHandlerFailsReadCompleted) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  net::URLRequestStatus old_handler_status;
+  size_t old_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> old_handler(new TestResourceHandler(
+      &old_handler_status, &old_handler_final_bytes_read));
+  scoped_refptr<net::IOBuffer> old_buffer = old_handler.get()->buffer();
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::move(old_handler), request.get()));
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+
+  // Simulate the MimeSniffingResourceHandler buffering the data.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  bool defer = false;
+  EXPECT_TRUE(intercepting_handler->OnWillStart(GURL(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_TRUE(intercepting_handler->OnWillRead(&read_buffer, &buf_size, -1));
+
+  const char kData[] = "The data";
+  ASSERT_EQ(read_buffer.get(), old_buffer.get());
+  ASSERT_GT(static_cast<size_t>(buf_size), sizeof(kData));
+  memcpy(read_buffer->data(), kData, sizeof(kData));
+
+  // Simulate the MimeSniffingResourceHandler asking the
+  // InterceptingResourceHandler to switch to a new handler.
+  net::URLRequestStatus new_handler_status;
+  size_t new_handler_final_bytes_read = 0;
+  std::unique_ptr<TestResourceHandler> new_handler(new TestResourceHandler(
+      &new_handler_status, &new_handler_final_bytes_read,
+      true,     // on_response_started
+      true,     // on_will_read
+      false));  // on_read_completed
+  intercepting_handler->UseNewHandler(std::move(new_handler), std::string());
+
+  // The response is received.
+  EXPECT_TRUE(intercepting_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_FALSE(defer);
+  EXPECT_EQ(net::URLRequestStatus::CANCELED, old_handler_status.status());
+  EXPECT_EQ(net::ERR_ABORTED, old_handler_status.error());
+
+  // The read is replayed by the MimeSniffingResourceHandler. The new handler
+  // should tell the caller to fail.
+  EXPECT_FALSE(intercepting_handler->OnReadCompleted(sizeof(kData), &defer));
+  EXPECT_FALSE(defer);
+}
+
+}  // namespace
+
+}  // namespace content