When InterceptingResourceHandler swaps in a handler, call OnWillStart.

The new ResourceHandler's OnWillStart was never being called, which
violates the ResourceHandler's API contract, and has caused at least one
crash previously (Though that fixed by another CL).

BUG=650717

Review-Url: https://codereview.chromium.org/2436163002
Cr-Commit-Position: refs/heads/master@{#427183}

content/browser/loader/intercepting_resource_handler.cc

@@ -8,6 +8,7 @@
 #include "base/strings/string_util.h"
 #include "content/public/common/resource_response.h"
 #include "net/base/io_buffer.h"
+#include "net/url_request/url_request.h"
 
 namespace content {
 
@@ -175,7 +176,10 @@ bool InterceptingResourceHandler::DoLoop(bool* defer) {
       case State::PASS_THROUGH:
         NOTREACHED();
         break;
-      case State::NOTIFYING_ON_RESPONSE_STARTED_TO_NEW_HANDLER:
+      case State::SENDING_ON_WILL_START_TO_NEW_HANDLER:
+        result = SendOnResponseStartedToNewHandler(defer);
+        break;
+      case State::SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER:
         if (first_read_buffer_double_) {
           // OnWillRead has been called, so copying the data from
           // |first_read_buffer_double_| to |first_read_buffer_| will be needed
@@ -239,7 +243,13 @@ bool InterceptingResourceHandler::SendPayloadToOldHandler(bool* defer) {
   DCHECK(!*defer);
 
   next_handler_ = std::move(new_handler_);
-  state_ = State::NOTIFYING_ON_RESPONSE_STARTED_TO_NEW_HANDLER;
+  state_ = State::SENDING_ON_WILL_START_TO_NEW_HANDLER;
+  return next_handler_->OnWillStart(request()->url(), defer);
+}
+
+bool InterceptingResourceHandler::SendOnResponseStartedToNewHandler(
+    bool* defer) {
+  state_ = State::SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER;
   return next_handler_->OnResponseStarted(response_.get(), defer);
 }
 

content/browser/loader/intercepting_resource_handler.h

@@ -81,11 +81,17 @@ class CONTENT_EXPORT InterceptingResourceHandler
     // Resume().
     SENDING_PAYLOAD_TO_OLD_HANDLER,
 
-    // The InterceptingResourcHandler is notifying OnResponseStarted to the new
-    // handler and waiting for its completion via Resume(). After the
-    // completion, the InterceptingResourcHandler will transit to
+    // The InterceptingResourcHandler is calling the new handler's
+    // OnResponseStarted method and waiting for its completion via Resume().
+    // After completion, the InterceptingResourceHandler will transition to
+    // SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER on success.
+    SENDING_ON_WILL_START_TO_NEW_HANDLER,
+
+    // The InterceptingResourcHandler is calling the new handler's
+    // OnResponseStarted method and waiting for its completion via Resume().
+    // After completion, the InterceptingResourceHandler will transition to
     // WAITING_FOR_ON_READ_COMPLETED on success.
-    NOTIFYING_ON_RESPONSE_STARTED_TO_NEW_HANDLER,
+    SENDING_ON_RESPONSE_STARTED_TO_NEW_HANDLER,
 
     // The InterceptingResourcHandler is waiting for OnReadCompleted to be
     // called.
@@ -110,7 +116,7 @@ class CONTENT_EXPORT InterceptingResourceHandler
   // The return value and |defer| has the same meaning as DoLoop.
   bool SendPayloadToOldHandler(bool* defer);
   bool SendFirstReadBufferToNewHandler(bool* defer);
-  bool SendCompletionToOldHandler(bool* defer);
+  bool SendOnResponseStartedToNewHandler(bool* defer);
 
   State state_ = State::STARTING;