Break apart header files.

Create libart-gtest for common runtime and compiler gtest routines.
Rename CompilerCallbacksImpl that is quick compiler specific.
Rename trace clock source constants to not use the overloaded profiler term.

Change-Id: I4aac4bdc7e7850c68335f81e59a390133b54e933
diff --git a/runtime/globals.h b/runtime/globals.h
index 3a906f1..1d9f22c 100644
--- a/runtime/globals.h
+++ b/runtime/globals.h
@@ -105,6 +105,19 @@
 // If true, references within the heap are poisoned (negated).
 static constexpr bool kPoisonHeapReferences = false;
 
+// Kinds of tracing clocks.
+enum TraceClockSource {
+  kTraceClockSourceThreadCpu,
+  kTraceClockSourceWall,
+  kTraceClockSourceDual,  // Both wall and thread CPU clocks.
+};
+
+#if defined(HAVE_POSIX_CLOCKS)
+static constexpr TraceClockSource kDefaultTraceClockSource = kTraceClockSourceDual;
+#else
+static constexpr TraceClockSource kDefaultTraceClockSource = kTraceClockSourceWall;
+#endif
+
 }  // namespace art
 
 #endif  // ART_RUNTIME_GLOBALS_H_