Adds counter for snapshot decompression time

I'm in the process of evaluating impact of v8 snapshot and
would like to understand the amount of time spend decompressing.

BUG=chromium:1257321
TEST=none

Change-Id: I122a2151e48f61db3352da56763e3e66f7415efe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3256006
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77661}

src/logging/counters-definitions.h

@@ -130,7 +130,9 @@ namespace internal {
   HT(compile_script, V8.CompileScriptMicroSeconds, 1000000, MICROSECOND)      \
   /* Time for lazily compiling Wasm functions. */                             \
   HT(wasm_lazy_compile_time, V8.WasmLazyCompileTimeMicroSeconds, 100000000,   \
-     MICROSECOND)
+     MICROSECOND)                                                             \
+  /* Total time to decompress snapshots. */                                   \
+  HT(snapshot_decompress, V8.SnapshotDecompress, 10000000, MICROSECOND)
 
 #define NESTED_TIMED_HISTOGRAM_LIST_SLOW(HT)                               \
   /* Total V8 time (including JS and runtime calls, exluding callbacks) */ \

src/snapshot/snapshot-data.cc

@@ -7,10 +7,6 @@
 #include "src/common/assert-scope.h"
 #include "src/snapshot/serializer.h"
 
-#ifdef V8_SNAPSHOT_COMPRESSION
-#include "src/snapshot/snapshot-compression.h"
-#endif
-
 namespace v8 {
 namespace internal {
 

src/snapshot/snapshot.cc

@@ -11,6 +11,7 @@
 #include "src/execution/isolate-inl.h"
 #include "src/heap/safepoint.h"
 #include "src/init/bootstrapper.h"
+#include "src/logging/counters-scopes.h"
 #include "src/logging/runtime-call-stats-scope.h"
 #include "src/objects/code-kind.h"
 #include "src/objects/js-regexp-inl.h"
@@ -173,9 +174,18 @@ bool Snapshot::Initialize(Isolate* isolate) {
   base::Vector<const byte> shared_heap_data =
       SnapshotImpl::ExtractSharedHeapData(blob);
 
+#ifdef V8_SNAPSHOT_COMPRESSION
+  base::Optional<NestedTimedHistogramScope> decompress_histogram;
+  if (base::TimeTicks::IsHighResolution()) {
+    decompress_histogram.emplace(isolate->counters()->snapshot_decompress());
+  }
+#endif
   SnapshotData startup_snapshot_data(MaybeDecompress(startup_data));
   SnapshotData read_only_snapshot_data(MaybeDecompress(read_only_data));
   SnapshotData shared_heap_snapshot_data(MaybeDecompress(shared_heap_data));
+#ifdef V8_SNAPSHOT_COMPRESSION
+  decompress_histogram.reset();
+#endif
 
   bool success = isolate->InitWithSnapshot(
       &startup_snapshot_data, &read_only_snapshot_data,