removes two snapshot related histograms

The experiment has been would down, so these can be removed.
This effectively reverts these two commits:

https://chromium-review.googlesource.com/c/v8/v8/+/3271389
https://chromium-review.googlesource.com/c/v8/v8/+/3256006

chrome side here:
https://chromium-review.googlesource.com/c/chromium/src/+/3399313

BUG=chromium:1257321
TEST=none

Change-Id: I5e9e4e7f56a6f19159d1c8c20c5a1fe5ed2859fb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3399226Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78685}

src/logging/counters-definitions.h

@@ -137,11 +137,6 @@ namespace internal {
   /* Time for lazily compiling Wasm functions. */                             \
   HT(wasm_lazy_compile_time, V8.WasmLazyCompileTimeMicroSeconds, 100000000,   \
      MICROSECOND)                                                             \
-  /* Total time to decompress isolate snapshot. */                            \
-  HT(snapshot_decompress, V8.SnapshotDecompress, 10000000, MICROSECOND)       \
-  /* Time to decompress context snapshot. */                                  \
-  HT(context_snapshot_decompress, V8.ContextSnapshotDecompress, 10000000,     \
-     MICROSECOND)                                                             \
   HT(wasm_compile_after_deserialize,                                          \
      V8.WasmCompileAfterDeserializeMilliSeconds, 1000000, MILLISECOND)
 

src/snapshot/snapshot.cc

@@ -11,7 +11,6 @@
 #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"
@@ -176,20 +175,11 @@ 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(isolate, startup_data));
   SnapshotData read_only_snapshot_data(
       MaybeDecompress(isolate, read_only_data));
   SnapshotData shared_heap_snapshot_data(
       MaybeDecompress(isolate, shared_heap_data));
-#ifdef V8_SNAPSHOT_COMPRESSION
-  decompress_histogram.reset();
-#endif
 
   bool success = isolate->InitWithSnapshot(
       &startup_snapshot_data, &read_only_snapshot_data,
@@ -215,20 +205,10 @@ MaybeHandle<Context> Snapshot::NewContextFromSnapshot(
   bool can_rehash = ExtractRehashability(blob);
   base::Vector<const byte> context_data = SnapshotImpl::ExtractContextData(
       blob, static_cast<uint32_t>(context_index));
-  base::Optional<SnapshotData> snapshot_data;
-  {
-#ifdef V8_SNAPSHOT_COMPRESSION
-    base::Optional<NestedTimedHistogramScope> decompress_histogram;
-    if (base::TimeTicks::IsHighResolution()) {
-      decompress_histogram.emplace(
-          isolate->counters()->context_snapshot_decompress());
-    }
-#endif
-    snapshot_data.emplace(MaybeDecompress(isolate, context_data));
-  }
+  SnapshotData snapshot_data(MaybeDecompress(isolate, context_data));
 
   MaybeHandle<Context> maybe_result = ContextDeserializer::DeserializeContext(
-      isolate, &(*snapshot_data), can_rehash, global_proxy,
+      isolate, &snapshot_data, can_rehash, global_proxy,
       embedder_fields_deserializer);
 
   Handle<Context> result;