[Windows] Release page metafile after printing to GDI API

Printing on Windows involves a two-step process, first converting pages
to the Windows metafile format (EMF) and then later playing that
metafile to print to the destination device.

The PrintedPage objects which contain this metafile data are retained
in the PrintedDocument until the document completes.  This has caused
the extra metafile representation to stay in memory well after it's
required lifetime has passed.  For jobs with many pages that include
full page rasters this triggers a memory spike that subsides only once
the last page is sent and the document is destroyed.

Avoid such memory spikes by dropping the PrintedPage object from the
document as soon as the page has been rendered to the destination, so
that its destructor can run and release the associated |metafile_|
memory.

Bug: 1031438
Change-Id: If6ff81f63e11989bc7ef1b341ee37be0cd8d4af7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975993Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Alan Screen <awscreen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726671}

chrome/browser/printing/print_job.cc

@@ -475,6 +475,7 @@ void PrintJob::OnNotifyPrintJobEvent(const JobEventDetails& event_details) {
         pdf_conversion_state_->OnPageProcessed(
             base::BindRepeating(&PrintJob::OnPdfPageConverted, this));
       }
+      document_->DropPage(event_details.page());
       break;
 #endif  // defined(OS_WIN)
     default: {

printing/printed_document.cc

@@ -156,6 +156,14 @@ scoped_refptr<PrintedPage> PrintedDocument::GetPage(int page_number) {
   }
   return page;
 }
+
+void PrintedDocument::DropPage(const PrintedPage* page) {
+  base::AutoLock lock(lock_);
+  PrintedPages::const_iterator it =
+      mutable_.pages_.find(page->page_number() - 1);
+  DCHECK_EQ(page, it->second.get());
+  mutable_.pages_.erase(it);
+}
 #endif  // defined(OS_WIN)
 
 void PrintedDocument::SetDocument(std::unique_ptr<MetafilePlayer> metafile,

printing/printed_document.h

@@ -60,6 +60,10 @@ class PRINTING_EXPORT PrintedDocument
   // requests to have this page be rendered and returns NULL.
   // Note: locks for a short amount of time.
   scoped_refptr<PrintedPage> GetPage(int page_number);
+
+  // Drop the specified page's reference for the particular page number.
+  // Note: locks for a short amount of time.
+  void DropPage(const PrintedPage* page);
 #endif  // defined(OS_WIN)
 
   // Sets the document data. Note: locks for a short amount of time.