Fix for race condition where print preview hangs when attempting to print a PDF that hasn't loaded.

chrome/renderer/printing/print_web_view_helper.cc

Index: chrome/renderer/printing/print_web_view_helper.cc
diff --git a/chrome/renderer/printing/print_web_view_helper.cc b/chrome/renderer/printing/print_web_view_helper.cc
index 777eb69fa183c52236578b34969c60e803511b5e..868a72bce48431d29d49235a4b968874ca169442 100644
--- a/chrome/renderer/printing/print_web_view_helper.cc
+++ b/chrome/renderer/printing/print_web_view_helper.cc
@@ -820,7 +820,12 @@ void PrintWebViewHelper::DidStartLoading() {
 
 void PrintWebViewHelper::DidStopLoading() {
   is_loading_ = false;
-  ShowScriptedPrintPreview();
+  if (request_print_preview_closure_.is_null()) {
+    ShowScriptedPrintPreview();

[Vitaly Buka (NO REVIEWS), 2014/08/05 06:05:06]

please remove ShowScriptedPrintPreview() from here use
request_print_preview_closure_ to call it.

request_print_preview_closure_ -> on_stop_loading_closure_ ?

[ivandavid, 2014/08/05 19:30:17]

Done.

+  } else {
+    request_print_preview_closure_.Run();
+    request_print_preview_closure_.Reset();
+  }
 }
 
 // Prints |frame| which called window.print().
@@ -1725,6 +1730,17 @@ void PrintWebViewHelper::RequestPrintPreview(PrintPreviewRequestType type) {
       return;
     }
     case PRINT_PREVIEW_USER_INITIATED_ENTIRE_FRAME: {

[ivandavid, 2014/07/29 20:02:51]

I encountered a similar problem to the one described in the bug when I was
working on a browser test that was printing PDFs. When I ran the browser test,
print preview would hang and just say 'Loading Preview...'. After some
investigation, it seemed like the problem that RequestPrintPreview() would be
called after DidStartLoading(), but before DidStopLoading(). So I modified the
code to cause it to wait for DidStopLoading() to be called to actually call
RequestPrintPreview() with the correct parameters and it fixed my problem. I was
only able to replicate this bug with the case
|PRINT_PREVIEW_USER_INITIATED_ENTIRE_FRAME|, therefore, I put the code there.

[Vitaly Buka (NO REVIEWS), 2014/08/05 05:49:57]

My understanding is that it's by design.
is_loading_ should be checked only for scripted preview.

For user initiated preview of web page it should be called immediately.
Page could be loading continuously for significant time, still user may wish to
print already loaded content.

Still maybe it's OK to have this exception for plugins. 
So it needs GetPlugin() check here like in case above.

On 2014/07/29 20:02:51, ivandavid wrote:

[ivandavid, 2014/08/05 19:30:17]

Done.

+      // If |is_loading_| is true and the function proceeds, Print Preview will
+      // hang. Save |type| and call this function when DidStopLoading() is
+      // called, ie. right when |is_loading_| is set to false.
+      if (is_loading_) {
+        request_print_preview_closure_ =
+            base::Bind(&PrintWebViewHelper::RequestPrintPreview,
+                       base::Unretained(this),
+                       type);
+        return;
+      }
+
       break;
     }
     case PRINT_PREVIEW_USER_INITIATED_SELECTION: {