Adds PrintingContext implementation stub for Android.

chrome/browser/printing/printing_message_filter.cc

Index: chrome/browser/printing/printing_message_filter.cc
diff --git a/chrome/browser/printing/printing_message_filter.cc b/chrome/browser/printing/printing_message_filter.cc
index 35b4074328de8ba4ec5e2cdce26e9c18c0654bf4..bb381f39db82bfc04768b9c803bda6a7058e35e8 100644
--- a/chrome/browser/printing/printing_message_filter.cc
+++ b/chrome/browser/printing/printing_message_filter.cc
@@ -32,6 +32,10 @@
 #include "chrome/browser/printing/print_dialog_cloud.h"
 #endif
 
+#if defined(OS_ANDROID)
+#include "chrome/browser/printing/print_view_manager_basic.h"
+#endif
+
 using content::BrowserThread;
 
 namespace {
@@ -100,6 +104,11 @@ void PrintingMessageFilter::OverrideThreadForMessage(
       message.type() == PrintHostMsg_TempFileForPrintingWritten::ID) {
     *thread = BrowserThread::FILE;
   }
+#elif defined(OS_ANDROID)
+  if (message.type() == PrintHostMsg_AllocateTempFileForPrinting::ID ||
+      message.type() == PrintHostMsg_TempFileForPrintingWritten::ID) {
+    *thread = BrowserThread::UI;
+  }
 #endif
 }
 
@@ -110,7 +119,7 @@ bool PrintingMessageFilter::OnMessageReceived(const IPC::Message& message,
 #if defined(OS_WIN)
     IPC_MESSAGE_HANDLER(PrintHostMsg_DuplicateSection, OnDuplicateSection)
 #endif
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
     IPC_MESSAGE_HANDLER(PrintHostMsg_AllocateTempFileForPrinting,
                         OnAllocateTempFileForPrinting)
     IPC_MESSAGE_HANDLER(PrintHostMsg_TempFileForPrintingWritten,
@@ -141,9 +150,13 @@ void PrintingMessageFilter::OnDuplicateSection(
 }
 #endif
 
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
 void PrintingMessageFilter::OnAllocateTempFileForPrinting(
-    base::FileDescriptor* temp_file_fd, int* sequence_number) {
+    int render_view_id,
+    base::FileDescriptor* temp_file_fd,
+    int* sequence_number) {
+#if defined(OS_CHROMEOS)
+  // TODO(thestig): Use |render_view_id| for Chrome OS.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   temp_file_fd->fd = *sequence_number = -1;
   temp_file_fd->auto_close = false;
@@ -166,10 +179,21 @@ void PrintingMessageFilter::OnAllocateTempFileForPrinting(
       }
     }
   }
+#elif defined(OS_ANDROID)
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  content::WebContents* wc = GetWebContentsForRenderView(render_view_id);
+  printing::PrintViewManagerBasic* print_view_manager =
+      printing::PrintViewManagerBasic::FromWebContents(wc);
+  // The file descriptor is originally created in & passed from the Android
+  // side, and it will handle the closing.
+  temp_file_fd->auto_close = false;

[Lei Zhang, 2013/08/15 01:31:05]

So after you hand off the fd to the renderer, and the renderer crashes, aren't
you leaking a fd? Since you are not auto closing, you probably need to do a
little more work to prevent fd leaks.

[whywhat, 2013/08/15 22:41:43]

How is the browser notified when the renderer crashed? We need to handle this
case and notify the owner of the FD.

[Lei Zhang, 2013/08/15 23:18:01]

PrintViewManagerBase -> content::WebContentsObserver ->
content::WebContentsObserverRenderProcessGone(). You probably want to notify the
upper layer and set the fd to -1 in PrintViewManagerBase.

+  temp_file_fd->fd = print_view_manager->GetFileDescriptor().fd;
+#endif
 }
 
 void PrintingMessageFilter::OnTempFileForPrintingWritten(int render_view_id,
                                                          int sequence_number) {
+#if defined(OS_CHROMEOS)
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   SequenceToPathMap* map = &g_printing_file_descriptor_map.Get().map;
   SequenceToPathMap::iterator it = map->find(sequence_number);
@@ -185,8 +209,18 @@ void PrintingMessageFilter::OnTempFileForPrintingWritten(int render_view_id,
 
   // Erase the entry in the map.
   map->erase(it);
+#elif defined(OS_ANDROID)
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  content::WebContents* wc = GetWebContentsForRenderView(render_view_id);
+  printing::PrintViewManagerBasic* print_view_manager =
+      printing::PrintViewManagerBasic::FromWebContents(wc);
+  // Invalidate the file descriptor so it doesn't accidentally get reused.
+  print_view_manager->SetFileDescriptor(base::FileDescriptor(-1, false));

[Lei Zhang, 2013/08/15 01:31:05]

Don't you need to do something here to tell the upper layers the renderer is
done writing and it is time to close the fd and send the result out to the
printer?

[whywhat, 2013/08/15 22:41:43]

We could use the fd as the key here. When fd is created, we remember it on the
Java side in a singleton mapping the fd to the fd owner.
From this method we'd call a static Java method via JNI in PrintingContext that
would find the fd owner and notify it.

[Lei Zhang, 2013/08/15 23:18:01]

I'm just trying to understand if that's something you can do from here, where
the renderer is explicitly telling you, "hey I'm done" versus if you need the
rest of the printing system to chew though it and get to
PrintingContext::DocumentDone() somehow.

I mentioned to Cihat the idea of just calling some dummy function here. How the
dummy function is implemented in Clank is up to you. To me, it feels better to
handle it here. The fd comes in at the chrome/ layer via
PrintViewManagerBasic::SetFileDescriptor() somehow, and you can reply at the
chrome/ layer via the dummy function.

+#endif
 }
+#endif  // defined(OS_CHROMEOS) || defined(OS_ANDROID)
 
+#if defined(OS_CHROMEOS)
 void PrintingMessageFilter::CreatePrintDialogForFile(
     int render_view_id,
     const base::FilePath& path) {