mojo: kill app_thread before unloading main app library and add tests

mojo/shell/in_process_dynamic_service_runner.cc

Index: mojo/shell/in_process_dynamic_service_runner.cc
diff --git a/mojo/shell/in_process_dynamic_service_runner.cc b/mojo/shell/in_process_dynamic_service_runner.cc
index 0d80d4096acdc13c8e526104d4604adff2405b40..31e558c3d0c8105befdf6d48f56f14380762b7e4 100644
--- a/mojo/shell/in_process_dynamic_service_runner.cc
+++ b/mojo/shell/in_process_dynamic_service_runner.cc
@@ -9,7 +9,6 @@
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop_proxy.h"
-#include "base/scoped_native_library.h"
 #include "mojo/public/platform/native/system_thunks.h"
 
 namespace mojo {
@@ -53,16 +52,15 @@ void InProcessDynamicServiceRunner::Run() {
 
   do {
     base::NativeLibraryLoadError error;
-    base::ScopedNativeLibrary app_library(
-        base::LoadNativeLibrary(app_path_, &error));
-    if (!app_library.is_valid()) {
+    app_library_.Reset(base::LoadNativeLibrary(app_path_, &error));
+    if (!app_library_.is_valid()) {
       LOG(ERROR) << "Failed to load app library (error: " << error.ToString()
                  << ")";
       break;
     }
 
     MojoSetSystemThunksFn mojo_set_system_thunks_fn =
-        reinterpret_cast<MojoSetSystemThunksFn>(app_library.GetFunctionPointer(
+        reinterpret_cast<MojoSetSystemThunksFn>(app_library_.GetFunctionPointer(
             "MojoSetSystemThunks"));
     if (mojo_set_system_thunks_fn) {
       MojoSystemThunks system_thunks = MojoMakeSystemThunks();
@@ -84,7 +82,7 @@ void InProcessDynamicServiceRunner::Run() {
 
     typedef MojoResult (*MojoMainFunction)(MojoHandle);
     MojoMainFunction main_function = reinterpret_cast<MojoMainFunction>(
-        app_library.GetFunctionPointer("MojoMain"));
+        app_library_.GetFunctionPointer("MojoMain"));
     if (!main_function) {
       LOG(ERROR) << "Entrypoint MojoMain not found";
       break;
@@ -94,6 +92,10 @@ void InProcessDynamicServiceRunner::Run() {
     MojoResult result = main_function(service_handle_.release().value());
     if (result < MOJO_RESULT_OK)
       LOG(ERROR) << "MojoMain returned an error: " << result;
+ // TODO(tim): Remove this ugly hack.

[darin (slow to review), 2014/07/19 21:18:00]

nit: can you explain what this ugly hack is achieving? it is not obvious.

[tim (not reviewing), 2014/07/19 21:59:42]

Sorry about that. What was happening was:

What's happening here is
* chromium-based apps like network_service have their own copy of base
* binding the shell_handle in MojoMains spins up a HandleWatcher
thread which registers some TLS data
* the destructor for that data points to a function in copy 2 of base::
* the app finishes up
* dlclose() the DSO (bye bye copy 2 of base)
* thread exits, kaboom

For shared library builds this was actually working because the pointer to the
static base:: function is still mapped. For static builds, it's gone.  If we do
*not* Reset the library here and let the thread terminate first, all is good.

I called it an "ugly hack" because of the #ifdef COMPONENT_BUILD... but as
discussed offline perhaps this is what we should do in all cases. I can see if I
can clean things up with that in mind.

+#if defined(COMPONENT_BUILD)
+    app_library_.Reset(base::NativeLibrary());
+#endif
   } while (false);
 
   bool success = app_completed_callback_runner_.Run();