Fix JDWP tests after ArtMethod change

Fixes Throwable::GetStackDepth for exception event detection after
internal stack trace representation change.

Adds missing ArtMethod::GetInterfaceMethodIfProxy call in case of
proxy method.

Bug: 19264997
Change-Id: I363e293796848c3ec491c963813f62d868da44d2
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 89e3467..65999f7 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -1583,7 +1583,7 @@
 
   bool Init(int depth)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    // Allocate method trace with an extra slot that will hold the PC trace
+    // Allocate method trace with format [method pointers][pcs].
     auto* cl = Runtime::Current()->GetClassLinker();
     trace_ = cl->AllocPointerArray(self_, depth * 2);
     if (trace_ == nullptr) {