ART: Clean up field initialization

Add explicit field initialization to default value where necessary.
Also clean up interpreter intrinsics header.

Test: m
Change-Id: I7a850ac30dcccfb523a5569fb8400b9ac892c8e5
diff --git a/runtime/base/arena_allocator.cc b/runtime/base/arena_allocator.cc
index 5aede38..e763e43 100644
--- a/runtime/base/arena_allocator.cc
+++ b/runtime/base/arena_allocator.cc
@@ -166,7 +166,7 @@
   MEMORY_TOOL_MAKE_NOACCESS(ptr, size);
 }
 
-Arena::Arena() : bytes_allocated_(0), next_(nullptr) {
+Arena::Arena() : bytes_allocated_(0), memory_(nullptr), size_(0), next_(nullptr) {
 }
 
 class MallocArena FINAL : public Arena {
diff --git a/runtime/base/histogram-inl.h b/runtime/base/histogram-inl.h
index ca9a694..b28eb72 100644
--- a/runtime/base/histogram-inl.h
+++ b/runtime/base/histogram-inl.h
@@ -48,7 +48,8 @@
     : kAdjust(0),
       kInitialBucketCount(0),
       name_(name),
-      max_buckets_(0) {
+      max_buckets_(0),
+      sample_size_(0) {
 }
 
 template <class Value>