Restore "Add current rss and embedder name to Observatory"

runtime/bin/process_android.cc

Index: runtime/bin/process_android.cc
diff --git a/runtime/bin/process_android.cc b/runtime/bin/process_android.cc
index 66fc280523091c99fa593a120e872a8b9738e42e..9b307f3ed6fa57367db774cc5be6bb100de90a8d 100644
--- a/runtime/bin/process_android.cc
+++ b/runtime/bin/process_android.cc
@@ -859,25 +859,27 @@ intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }
 
+static void SaveErrorAndClose(FILE* file) {
+  int actual_errno = errno;
+  fclose(file);
+  errno = actual_errno;
+}
+
 int64_t Process::CurrentRSS() {
   // The second value in /proc/self/statm is the current RSS in pages.
-  File* statm = File::Open("/proc/self/statm", File::kRead);
+  // It is not possible to use getrusage() because the interested fields are not
+  // implemented by the linux kernel.
+  FILE* statm = fopen("/proc/self/statm", "r");
   if (statm == NULL) {
     return -1;
   }
-  RefCntReleaseScope<File> releaser(statm);
-  const intptr_t statm_length = 1 * KB;
-  void* buffer = reinterpret_cast<void*>(Dart_ScopeAllocate(statm_length));
-  const intptr_t statm_read = statm->Read(buffer, statm_length);
-  if (statm_read <= 0) {
-    return -1;
-  }
   int64_t current_rss_pages = 0;
-  int matches = sscanf(reinterpret_cast<char*>(buffer), "%*s%" Pd64 "",
-                       &current_rss_pages);
+  int matches = fscanf(statm, "%*s%" Pd64 "", &current_rss_pages);
   if (matches != 1) {
+    SaveErrorAndClose(statm);
     return -1;
   }
+  fclose(statm);
   return current_rss_pages * getpagesize();
 }