base::Hash and base::Hasher

Rename base::Hash to base::Hasher to more accurately reflect what it does and add base::Hash, which serves as a counterpart for std::hash
(but with better hashing for ints).

R=lalitm@google.com

Change-Id: If586465b90f550a1a538158e5afbc59dd4ee0a3e
diff --git a/src/traceconv/pprof_builder.cc b/src/traceconv/pprof_builder.cc
index a5f724f..9dd2517 100644
--- a/src/traceconv/pprof_builder.cc
+++ b/src/traceconv/pprof_builder.cc
@@ -115,7 +115,7 @@
 template <>
 struct std::hash<Function> {
   size_t operator()(const Function& loc) const {
-    perfetto::base::Hash hasher;
+    perfetto::base::Hasher hasher;
     hasher.Update(loc.name_id.raw_id());
     hasher.Update(loc.system_name_id.raw_id());
     hasher.Update(loc.filename_id.raw_id());
@@ -126,7 +126,7 @@
 template <>
 struct std::hash<Location> {
   size_t operator()(const Location& loc) const {
-    perfetto::base::Hash hasher;
+    perfetto::base::Hasher hasher;
     hasher.Update(loc.mapping_id);
     hasher.Update(loc.single_function_id);
     for (auto line : loc.inlined_functions) {