Convert 0 to nullptr in content using clang-tidy.

Bug: 778942
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
Change-Id: Iee6be84c23149c745b3afd6e6158764f92ccd17f
Reviewed-on: https://chromium-review.googlesource.com/732305
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Commit-Queue: Ivan Kotenkov <[email protected]>
Cr-Commit-Position: refs/heads/master@{#513138}
diff --git a/content/shell/browser/shell_download_manager_delegate.cc b/content/shell/browser/shell_download_manager_delegate.cc
index 48f79c8..ebefd9c 100644
--- a/content/shell/browser/shell_download_manager_delegate.cc
+++ b/content/shell/browser/shell_download_manager_delegate.cc
@@ -35,14 +35,14 @@
 namespace content {
 
 ShellDownloadManagerDelegate::ShellDownloadManagerDelegate()
-    : download_manager_(NULL),
+    : download_manager_(nullptr),
       suppress_prompting_(false),
       weak_ptr_factory_(this) {}
 
 ShellDownloadManagerDelegate::~ShellDownloadManagerDelegate() {
   if (download_manager_) {
-    download_manager_->SetDelegate(NULL);
-    download_manager_ = NULL;
+    download_manager_->SetDelegate(nullptr);
+    download_manager_ = nullptr;
   }
 }
 
@@ -56,7 +56,7 @@
   // Revoke any pending callbacks. download_manager_ et. al. are no longer safe
   // to access after this point.
   weak_ptr_factory_.InvalidateWeakPtrs();
-  download_manager_ = NULL;
+  download_manager_ = nullptr;
 }
 
 bool ShellDownloadManagerDelegate::DetermineDownloadTarget(