Adds support for UseDartApi vm test on MIPS.

runtime/vm/cpu_mips.cc

Index: runtime/vm/cpu_mips.cc
===================================================================
--- runtime/vm/cpu_mips.cc	(revision 21386)
+++ runtime/vm/cpu_mips.cc	(working copy)
@@ -7,6 +7,7 @@
 #if defined(TARGET_ARCH_MIPS)
 
 #if defined(HOST_ARCH_MIPS)
+#include <asm/cachectl.h> /* NOLINT */
 #include <sys/syscall.h>  /* NOLINT */
 #include <unistd.h>  /* NOLINT */
 #endif
@@ -16,7 +17,15 @@
 namespace dart {
 
 void CPU::FlushICache(uword start, uword size) {
-  UNIMPLEMENTED();
+#if defined(HOST_ARCH_MIPS)
+  int res;
+  // See http://www.linux-mips.org/wiki/Cacheflush_Syscall.
+  res = syscall(__NR_cacheflush, start, size, ICACHE);
+  ASSERT(res == 0);
+#else  // defined(HOST_ARCH_MIPS)
+  // When running in simulated mode we do not need to flush the ICache because
+  // we are not running on the actual hardware.
+#endif  // defined(HOST_ARCH_MIPS)
 }