Fuchsia: Add native symbol resolver. Small fixes.

runtime/vm/native_symbol_fuchsia.cc

Index: runtime/vm/native_symbol_fuchsia.cc
diff --git a/runtime/vm/native_symbol_fuchsia.cc b/runtime/vm/native_symbol_fuchsia.cc
index cb0f02a77300a1595b7617a530557d9bd1109c22..084c00b54eefda1b08e1294fe9fe5af35ea5b5b5 100644
--- a/runtime/vm/native_symbol_fuchsia.cc
+++ b/runtime/vm/native_symbol_fuchsia.cc
@@ -2,33 +2,41 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#include "vm/globals.h"
+#include "platform/globals.h"
 #if defined(TARGET_OS_FUCHSIA)
 
 #include "vm/native_symbol.h"
 
-#include "platform/assert.h"
+#include <dlfcn.h>  // NOLINT
 
 namespace dart {
 
 void NativeSymbolResolver::InitOnce() {
-  UNIMPLEMENTED();
 }
 
 
 void NativeSymbolResolver::ShutdownOnce() {
-  UNIMPLEMENTED();
 }
 
 
 char* NativeSymbolResolver::LookupSymbolName(uintptr_t pc, uintptr_t* start) {
-  UNIMPLEMENTED();
-  return NULL;
+  Dl_info info;
+  int r = dladdr(reinterpret_cast<void*>(pc), &info);
+  if (r == 0) {
+    return NULL;
+  }
+  if (info.dli_sname == NULL) {
+    return NULL;
+  }
+  if (start != NULL) {
+    *start = reinterpret_cast<uintptr_t>(info.dli_saddr);
+  }
+  return strdup(info.dli_sname);
 }
 
 
 void NativeSymbolResolver::FreeSymbolName(char* name) {
-  UNIMPLEMENTED();
+  free(name);
 }
 
 }  // namespace dart