Fix printing on Windows when sandbox is enabled

Auditors:  @bridiver

This makes it closer to how it works in Chromium and fixes the forever spooling problem on Windows.

The old way worked when the sandbox was disabled but failed on the call for shared_buf.CreateAndMapAnonymous when the sandbox was enabled

This also fixes a handle leak which Chromium already had fixed.

chromium_src/chrome/renderer/printing/print_web_view_helper_pdf_win.cc

@@ -113,6 +113,7 @@ bool PrintWebViewHelper::PrintPagesNative(blink::WebFrame* frame,
     printed_page_params.content_area = content_area_in_dpi[i];
     Send(new PrintHostMsg_DidPrintPage(routing_id(), printed_page_params));
     // Send the rest of the pages with an invalid metafile handle.
+    printed_page_params.metafile_data_handle.Close();
     printed_page_params.metafile_data_handle = base::SharedMemoryHandle();
   }
   return true;
@@ -198,22 +199,19 @@ bool PrintWebViewHelper::CopyMetafileDataToSharedMem(
   if (buf_size == 0)
     return false;
 
-  base::SharedMemory shared_buf;
-  // Allocate a shared memory buffer to hold the generated metafile data.
-  if (!shared_buf.CreateAndMapAnonymous(buf_size))
+  std::unique_ptr<base::SharedMemory> shared_buf(
+      content::RenderThread::Get()->HostAllocateSharedMemoryBuffer(buf_size));
+  if (!shared_buf)
     return false;
 
-  // Copy the bits into shared memory.
-  if (!metafile.GetData(shared_buf.memory(), buf_size))
+  if (!shared_buf->Map(buf_size))
     return false;
 
-  if (!shared_buf.GiveToProcess(base::GetCurrentProcessHandle(),
-                                shared_mem_handle)) {
+  if (!metafile.GetData(shared_buf->memory(), buf_size))
     return false;
-  }
 
-  Send(new PrintHostMsg_DuplicateSection(routing_id(), *shared_mem_handle,
-                                         shared_mem_handle));
+  *shared_mem_handle =
+      base::SharedMemory::DuplicateHandle(shared_buf->handle());
   return true;
 }