Perform a sizet->int checked_cast in WebURLLoaderImpl::OnReceiveWebBlobData.

Fixes an error on my Windows build:
d:\src\chrome-git\src\components\html_viewer\web_url_loader_impl.cc(254) : error C2220: warning treated as error - no 'object' file generated
d:\src\chrome-git\src\components\html_viewer\web_url_loader_impl.cc(254) : warning C4267: 'argument' : conversion from 'size_t' to 'int', possible loss of data

BUG=NONE
TEST=Windows html_viewer build succeeds.
R=erg@chromium.org
TBR=sky@chromium.org

Review URL: https://codereview.chromium.org/1096243004

Cr-Commit-Position: refs/heads/master@{#326898}

components/html_viewer/web_url_loader_impl.cc

@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/thread_task_runner_handle.h"
 #include "components/html_viewer/blink_url_request_type_converters.h"
@@ -250,8 +251,8 @@ void WebURLLoaderImpl::OnReceiveWebBlobData(
 
   // Send a receive data for each blob item.
   for (size_t i = 0; i < items.size(); ++i) {
-    client_->didReceiveData(this, items[i]->data.data(), items[i]->data.size(),
-                            -1);
+    const int data_size = base::checked_cast<int>(items[i]->data.size());
+    client_->didReceiveData(this, items[i]->data.data(), data_size, -1);
   }
 
   // Send a closing finish.
@@ -270,7 +271,7 @@ void WebURLLoaderImpl::ReadMore() {
   if (rv == MOJO_RESULT_OK) {
     base::WeakPtr<WebURLLoaderImpl> self(weak_factory_.GetWeakPtr());
     client_->didReceiveData(this, static_cast<const char*>(buf), buf_size, -1);
-    // We may have been deleted durining didReceiveData.
+    // We may have been deleted during didReceiveData.
     if (!self)
       return;
     EndReadDataRaw(response_body_stream_.get(), buf_size);