Print more info in MarkSweep::VerifyRoot

Refactored old root callback to use a new class called RootInfo.
RootInfo contains all the relevant info related to the root
associated with the callback. The MarkSweep::VerifyRoot function
now uses this info to print the StackVisitor's described location
if the GC root is of the type kRootJavaFrame.

Some other cleanup.

Example output:
E/art     (12167): Tried to mark 0x123 not contained by any spaces
E/art     (12167): Attempting see if it's a bad root
E/art     (12167): Found invalid root: 0x123 with type RootJavaFrame
E/art     (12167): Location=Visiting method
'void java.lang.Runtime.gc()' at dex PC 0xffffffff (native PC 0x0)
vreg=0

(cherry picked from commit 12f7423a2bb4bfab76700d84eb6d4338d211983a)

Bug: 18588862
Change-Id: Ic5a2781f704e931265ffb3621c2eab4b2e25f60f
diff --git a/runtime/native/dalvik_system_VMRuntime.cc b/runtime/native/dalvik_system_VMRuntime.cc
index 471aa9c..599d97f 100644
--- a/runtime/native/dalvik_system_VMRuntime.cc
+++ b/runtime/native/dalvik_system_VMRuntime.cc
@@ -249,7 +249,7 @@
 typedef std::map<std::string, mirror::String*> StringTable;
 
 static void PreloadDexCachesStringsCallback(mirror::Object** root, void* arg,
-                                            uint32_t /*thread_id*/, RootType /*root_type*/)
+                                            const RootInfo& /*root_info*/)
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   StringTable& table = *reinterpret_cast<StringTable*>(arg);
   mirror::String* string = const_cast<mirror::Object*>(*root)->AsString();