Check if temp file was created before OnPageDone called

Broken utility process may send PageDone message before
browser asked for the page. In this case emf is not allocated yet
and browser will crash later on playback.

Renamed emf() to TakeEmf() to highlight changed ownership.

BUG=none

Review URL: https://codereview.chromium.org/1132393002

Cr-Commit-Position: refs/heads/master@{#329207}

chrome/browser/printing/pdf_to_emf_converter.cc

@@ -60,7 +60,9 @@ typedef scoped_ptr<base::File, BrowserThread::DeleteOnFileThread>
 class LazyEmf : public MetafilePlayer {
  public:
   LazyEmf(const scoped_refptr<RefCountedTempDir>& temp_dir, ScopedTempFile file)
-      : temp_dir_(temp_dir), file_(file.Pass()) {}
+      : temp_dir_(temp_dir), file_(file.Pass()) {
+    CHECK(file_);
+  }
   ~LazyEmf() override { Close(); }
 
   bool SafePlayback(HDC hdc) const override;
@@ -133,7 +135,7 @@ class PdfToEmfUtilityProcessHostClient
     const PdfToEmfConverter::GetPageCallback& callback() const {
       return callback_;
     }
-    ScopedTempFile emf() { return emf_.Pass(); }
+    ScopedTempFile TakeEmf() { return emf_.Pass(); }
     void set_emf(ScopedTempFile emf) { emf_ = emf.Pass(); }
 
    private:
@@ -398,10 +400,16 @@ void PdfToEmfUtilityProcessHostClient::OnPageDone(bool success,
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (get_page_callbacks_.empty())
     return OnFailed();
-  scoped_ptr<MetafilePlayer> emf;
   GetPageCallbackData& data = get_page_callbacks_.front();
-  if (success)
-    emf.reset(new LazyEmf(temp_dir_, data.emf().Pass()));
+  scoped_ptr<MetafilePlayer> emf;
+
+  if (success) {
+    ScopedTempFile temp_emf = data.TakeEmf();
+    if (!temp_emf)  // Unexpected message from utility process.
+      return OnFailed();
+    emf.reset(new LazyEmf(temp_dir_, temp_emf.Pass()));
+  }
+
   BrowserThread::PostTask(BrowserThread::UI,
                           FROM_HERE,
                           base::Bind(&PdfToEmfConverterImpl::RunCallback,