Bug 1235475 - Crash at the exception source when an exception is in native code; r=snorp

When we have a Java exception in native code, the Java stack in the
exception will not be very useful because the top frame is the native
entry point. In this case, the native stack is more useful. However,
currently we don't get a good native stack in this situation because we
go through Java when handling the exception, and the native stack we get
will have a lot of unknown frames inside libdvm or libart. This patch
makes us stay in native code when handling an uncaught exception from
native code, so that we get a good native stack.

widget/android/jni/Utils.cpp

@@ -8,6 +8,10 @@
 #include "AndroidBridge.h"
 #include "GeneratedJNIWrappers.h"
 
+#ifdef MOZ_CRASHREPORTER
+#include "nsExceptionHandler.h"
+#endif
+
 namespace mozilla {
 namespace jni {
 
@@ -129,23 +133,34 @@ bool ThrowException(JNIEnv *aEnv, const char *aClass,
     return !aEnv->ThrowNew(cls.Get(), aMessage);
 }
 
-void HandleUncaughtException(JNIEnv *aEnv)
+bool HandleUncaughtException(JNIEnv* aEnv)
 {
     MOZ_ASSERT(aEnv, "Invalid thread JNI env");
 
     if (!aEnv->ExceptionCheck()) {
-        return;
+        return false;
     }
 
+#ifdef DEBUG
+    aEnv->ExceptionDescribe();
+#endif
+
     Throwable::LocalRef e =
             Throwable::LocalRef::Adopt(aEnv->ExceptionOccurred());
     MOZ_ASSERT(e);
 
     aEnv->ExceptionClear();
-    widget::GeckoAppShell::HandleUncaughtException(nullptr, e);
+    String::LocalRef stack = widget::GeckoAppShell::HandleUncaughtException(e);
 
-    // Should be dead by now...
-    MOZ_CRASH("Failed to handle uncaught exception");
+#ifdef MOZ_CRASHREPORTER
+    if (stack) {
+        // GeckoAppShell wants us to annotate and trigger the crash reporter.
+        CrashReporter::AnnotateCrashReport(
+                NS_LITERAL_CSTRING("AuxiliaryJavaStack"), nsCString(stack));
+    }
+#endif // MOZ_CRASHREPORTER
+
+    return true;
 }
 
 namespace {