Add way to print JIT related info at shutdown

Added a runtime option called -XX:DumpJITInfoOnShutdown with prints
various interesting JIT statistics during the shutdown of the runtime
if enabled.

Example of running EvaluateAndApplyChanges with the option:
I art     : Code cache size=427KB data cache size=84KB num methods=1598
I art     : Start Dumping histograms for 1598 iterations for JIT timings
I art     : Compiling: Sum: 727.850ms 99% C.I. 135us-4402us Avg: 455.475us Max: 15567us
I art     : Verifying: Sum: 191.074ms 99% C.I. 19us-1450.500us Avg: 119.570us Max: 5142us
I art     : TrimMaps:  Sum: 62.053ms 99% C.I. 13us-199.374us Avg: 38.831us Max: 10058us
I art     : MakeExecutable:  Sum: 11.153ms 99% C.I. 4us-47us Avg: 6.979us Max: 47us
I art     : Initializing:  Sum: 7.991ms 99% C.I. 1us-49.781us Avg: 5us Max: 4852us
I art     : Done Dumping histograms

Bug: 17950037
Change-Id: I23538b24f947e5f6934f55579b8baa9d806eb3d5
diff --git a/runtime/jit/jit_code_cache.cc b/runtime/jit/jit_code_cache.cc
index 4ae4d57..4d367e0 100644
--- a/runtime/jit/jit_code_cache.cc
+++ b/runtime/jit/jit_code_cache.cc
@@ -77,6 +77,7 @@
   if (size > CodeCacheRemain()) {
     return nullptr;
   }
+  ++num_methods_;  // TODO: This is hacky but works since each method has exactly one code region.
   code_cache_ptr_ += size;
   return code_cache_ptr_ - size;
 }