Add UMA histograms to mojo leveldb env

components/leveldb/env_mojo.h

Index: components/leveldb/env_mojo.h
diff --git a/components/leveldb/env_mojo.h b/components/leveldb/env_mojo.h
index 8af9ef4aebcd0e0a8dfe927e291ef21ea56db948..569bcfe5ccb9e1eb0238acafa2571c46c229dfa8 100644
--- a/components/leveldb/env_mojo.h
+++ b/components/leveldb/env_mojo.h
@@ -7,6 +7,7 @@
 
 #include "components/filesystem/public/interfaces/directory.mojom.h"
 #include "components/leveldb/leveldb_mojo_proxy.h"
+#include "third_party/leveldatabase/env_chromium.h"
 #include "third_party/leveldatabase/src/include/leveldb/env.h"
 
 namespace leveldb {
@@ -16,7 +17,7 @@ namespace leveldb {
 // synchronous and block on responses from the filesystem service. That's fine
 // since, for the most part, they merely open files or check for a file's
 // existence.
-class MojoEnv : public leveldb::Env {
+class MojoEnv : public Env, public leveldb_env::UMALogger {
  public:
   MojoEnv(scoped_refptr<LevelDBMojoProxy> file_thread,
           LevelDBMojoProxy::OpaqueDir* dir);
@@ -50,6 +51,13 @@ class MojoEnv : public leveldb::Env {
   void StartThread(void (*function)(void* arg), void* arg) override;
 
  private:
+  void RecordErrorAt(leveldb_env::MethodID method) const override;
+  void RecordOSError(leveldb_env::MethodID method,
+                     base::File::Error error) const override;
+
+  void RecordFileError(leveldb_env::MethodID method,
+                       filesystem::mojom::FileError error) const;
+
   scoped_refptr<LevelDBMojoProxy> thread_;
   LevelDBMojoProxy::OpaqueDir* dir_;