Fix race condition with windowless plugin buffers. The problem, which is already fixed for Mac, is …

webkit/plugins/npapi/test/plugin_windowless_test.cc

Index: webkit/plugins/npapi/test/plugin_windowless_test.cc
===================================================================
--- webkit/plugins/npapi/test/plugin_windowless_test.cc	(revision 151213)
+++ webkit/plugins/npapi/test/plugin_windowless_test.cc	(working copy)
@@ -11,6 +11,8 @@
 #if defined(OS_MACOSX)
 #include <ApplicationServices/ApplicationServices.h>
 #include <Carbon/Carbon.h>
+#elif defined(TOOLKIT_GTK)
+#include <gdk/gdkx.h>
 #endif
 
 namespace NPAPIClient {
@@ -18,9 +20,14 @@
 // Remember the first plugin instance for tests involving multiple instances
 WindowlessPluginTest* g_other_instance = NULL;
 
+void OnFinishTest(void* data) {
+  static_cast<WindowlessPluginTest*>(data)->SignalTestCompleted();
+}
+
 WindowlessPluginTest::WindowlessPluginTest(NPP id,
                                            NPNetscapeFuncs *host_functions)
-    : PluginTest(id, host_functions) {
+    : PluginTest(id, host_functions),
+      paint_counter_(0) {
   if (!g_other_instance)
     g_other_instance = this;
 }
@@ -30,6 +37,8 @@
   return WM_PAINT == np_event->event;
 #elif defined(OS_MACOSX)
   return np_event->what == updateEvt;
+#elif defined(TOOLKIT_GTK)
+  return np_event->type == GraphicsExpose;
 #else
   NOTIMPLEMENTED();
   return false;
@@ -72,7 +81,6 @@
 }
 
 int16 WindowlessPluginTest::HandleEvent(void* event) {
-
   NPNetscapeFuncs* browser = NPAPIClient::PluginClient::HostFunctions();
 
   NPBool supports_windowless = 0;
@@ -86,6 +94,7 @@
 
   NPEvent* np_event = reinterpret_cast<NPEvent*>(event);
   if (IsPaintEvent(np_event)) {
+    paint_counter_++;
 #if defined(OS_WIN)
     HDC paint_dc = reinterpret_cast<HDC>(np_event->wParam);
     if (paint_dc == NULL) {
@@ -109,6 +118,19 @@
       ExecuteScriptDeleteInPaint(browser);
     } else if (test_name() == "multiple_instances_sync_calls") {
       MultipleInstanceSyncCalls(browser);
+    } else if (test_name() == "resize_during_paint") {
+      if (paint_counter_ == 1) {
+        // So that we get another paint later.
+        browser->invalidaterect(id(), NULL);
+      } else if (paint_counter_ == 2) {
+        // Do this in the second paint since that's asynchronous. The first will
+        // be async and WebKit will assert that style recalc doesn't occur while
+        // _it's_ painting (as opposed to the plugin).

[Tom Hudson, 2012/08/15 17:04:00]

Nit: I'd like to understand this, but I don't follow any of the comments in the
new code block here - perhaps I just don't have enough chromium test framework
background.

[jam, 2012/08/15 17:28:11]

my bad, I was lazy and wrote a comment that I myself would forget in a few weeks
:)

I've beefed this up, let me know if this is more understandable.

[Tom Hudson, 2012/08/15 17:59:04]

So there are two paints, and both are asynchronous?
The first is managed by WebKit, the second by the plugin?

The first sentence implies to me that the first paint isn't asynchronous, but
the second sentence immediately says it is.

[jam, 2012/08/15 18:22:22]

that was a typo, check out the update

+        ExecuteScriptResizeInPaint(browser);
+
+        // So that we can exit later.
+        browser->pluginthreadasynccall(id(), OnFinishTest, this);
+      }
     }
 #if defined(OS_MACOSX)
   } else if (IsWindowActivationEvent(np_event) &&
@@ -159,6 +181,11 @@
   SignalTestCompleted();
 }
 
+void WindowlessPluginTest::ExecuteScriptResizeInPaint(
+    NPNetscapeFuncs* browser) {
+  ExecuteScript(browser, id(), "ResizePluginWithinScript();", NULL);
+}
+
 void WindowlessPluginTest::MultipleInstanceSyncCalls(NPNetscapeFuncs* browser) {
   if (this == g_other_instance)
     return;