Small refactoring on downloaditemimpl

Remove BrowserThread and WebContents references

Bug: 803135
Change-Id: I791bbeb0bd3d52c497c7bad7d035aaac7440f588
Reviewed-on: https://chromium-review.googlesource.com/981328
Commit-Queue: Min Qin <qinmin@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546008}

content/browser/download/download_item_impl.h

@@ -16,6 +16,7 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "base/threading/thread_checker_impl.h"
 #include "base/time/time.h"
 #include "components/download/public/common/download_create_info.h"
 #include "components/download/public/common/download_destination_observer.h"
@@ -36,7 +37,6 @@ class DownloadJob;
 namespace content {
 class BrowserContext;
 class DownloadItemImplDelegate;
-class WebContents;
 
 // See download_item.h for usage.
 class CONTENT_EXPORT DownloadItemImpl
@@ -614,8 +614,7 @@ class CONTENT_EXPORT DownloadItemImpl
   // INTERRUPTED state.
   download::ResumeMode GetResumeMode() const;
 
-  // Helper method to get WebContents and BrowserContext of the DownloadItem.
-  WebContents* GetWebContents() const;
+  // Helper method to get BrowserContext of the DownloadItem.;
   BrowserContext* GetBrowserContext() const;
 
   static DownloadState InternalToExternalState(
@@ -777,6 +776,8 @@ class CONTENT_EXPORT DownloadItemImpl
   // Source of the download, used in metrics.
   download::DownloadSource download_source_ = download::DownloadSource::UNKNOWN;
 
+  THREAD_CHECKER(thread_checker_);
+
   base::WeakPtrFactory<DownloadItemImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemImpl);

content/browser/download/download_item_impl_delegate.cc

@@ -88,4 +88,7 @@ void DownloadItemImplDelegate::DownloadRemoved(DownloadItemImpl* download) {}
 void DownloadItemImplDelegate::AssertStateConsistent(
     DownloadItemImpl* download) const {}
 
+void DownloadItemImplDelegate::DownloadInterrupted(DownloadItemImpl* download) {
+}
+
 }  // namespace content

content/browser/download/download_item_impl_delegate.h

@@ -100,6 +100,9 @@ class CONTENT_EXPORT DownloadItemImplDelegate {
   // Assert consistent state for delgate object at various transitions.
   virtual void AssertStateConsistent(DownloadItemImpl* download) const;
 
+  // Called when the download is interrupted.
+  virtual void DownloadInterrupted(DownloadItemImpl* download);
+
  private:
   // For "Outlives attached DownloadItemImpl" invariant assertion.
   int count_;

content/browser/download/download_manager_impl.cc

@@ -845,6 +845,14 @@ void DownloadManagerImpl::DownloadRemoved(DownloadItemImpl* download) {
   downloads_.erase(download->GetId());
 }
 
+void DownloadManagerImpl::DownloadInterrupted(DownloadItemImpl* download) {
+  WebContents* web_contents = DownloadItemUtils::GetWebContents(download);
+  if (!web_contents) {
+    download::RecordDownloadCountWithSource(
+        download::INTERRUPTED_WITHOUT_WEBCONTENTS, download->download_source());
+  }
+}
+
 void DownloadManagerImpl::OnUrlDownloadHandlerCreated(
     download::UrlDownloadHandler::UniqueUrlDownloadHandlerPtr downloader) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);

content/browser/download/download_manager_impl.h

@@ -234,6 +234,7 @@ class CONTENT_EXPORT DownloadManagerImpl
   bool IsMostRecentDownloadItemAtFilePath(DownloadItemImpl* download) override;
   void ShowDownloadInShell(DownloadItemImpl* download) override;
   void DownloadRemoved(DownloadItemImpl* download) override;
+  void DownloadInterrupted(DownloadItemImpl* download) override;
 
   // Helper method to start or resume a download.
   void BeginDownloadInternal(