gin: Set V8 context snapshot as a default snapshot

Thanks to the change in V8 to make external reference table optional,
we can always use v8_context_snapshot.bin on platforms where it is
avaiable.

This CL sets the file as the default snapshot blob, and removes
setting snapshot in Isolate::CreateParam.


Bug: 764576, 789964
Change-Id: I16654eef810efcd0103e9a29659f4616c61f790b
Reviewed-on: https://chromium-review.googlesource.com/802654
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522662}

gin/BUILD.gn

@@ -4,6 +4,7 @@
 
 import("//testing/test.gni")
 import("//v8/gni/v8.gni")
+import("//tools/v8_context_snapshot/v8_context_snapshot.gni")
 
 component("gin") {
   sources = [
@@ -82,6 +83,9 @@ component("gin") {
       "$root_out_dir/natives_blob.bin",
       "$root_out_dir/snapshot_blob.bin",
     ]
+    if (use_v8_context_snapshot) {
+      data += [ "$root_out_dir/v8_context_snapshot.bin" ]
+    }
   }
 
   defines = [ "GIN_IMPLEMENTATION" ]
@@ -98,7 +102,10 @@ component("gin") {
     libs = [ "CoreFoundation.framework" ]
   }
 
-  configs += [ "//v8:external_startup_data" ]
+  configs += [
+    "//tools/v8_context_snapshot:use_v8_context_snapshot",
+    "//v8:external_startup_data",
+  ]
 }
 
 executable("gin_shell") {
@@ -115,7 +122,10 @@ executable("gin_shell") {
     "//v8",
   ]
 
-  configs += [ "//v8:external_startup_data" ]
+  configs += [
+    "//tools/v8_context_snapshot:use_v8_context_snapshot",
+    "//v8:external_startup_data",
+  ]
 }
 
 source_set("gin_test") {
@@ -142,10 +152,14 @@ source_set("gin_test") {
   ]
   deps = [
     "//base/test:test_support",
+    "//tools/v8_context_snapshot",
     "//v8",
   ]
 
-  configs += [ "//v8:external_startup_data" ]
+  configs += [
+    "//tools/v8_context_snapshot:use_v8_context_snapshot",
+    "//v8:external_startup_data",
+  ]
 }
 
 test("gin_unittests") {

gin/isolate_holder.cc

@@ -37,16 +37,12 @@ IsolateHolder::IsolateHolder(
 IsolateHolder::IsolateHolder(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     AccessMode access_mode)
-    : IsolateHolder(std::move(task_runner),
-                    access_mode,
-                    kAllowAtomicsWait,
-                    nullptr) {}
+    : IsolateHolder(std::move(task_runner), access_mode, kAllowAtomicsWait) {}
 
 IsolateHolder::IsolateHolder(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     AccessMode access_mode,
-    AllowAtomicsWaitMode atomics_wait_mode,
-    v8::StartupData* startup_data)
+    AllowAtomicsWaitMode atomics_wait_mode)
     : access_mode_(access_mode) {
   v8::ArrayBuffer::Allocator* allocator = g_array_buffer_allocator;
   CHECK(allocator) << "You need to invoke gin::IsolateHolder::Initialize first";
@@ -59,14 +55,6 @@ IsolateHolder::IsolateHolder(
   params.array_buffer_allocator = allocator;
   params.allow_atomics_wait = atomics_wait_mode == kAllowAtomicsWait;
   params.external_references = g_reference_table;
-
-  if (startup_data) {
-    CHECK(g_reference_table);
-    V8Initializer::GetV8ContextSnapshotData(startup_data);
-    if (startup_data->data) {
-      params.snapshot_blob = startup_data;
-    }
-  }
   isolate_ = v8::Isolate::New(params);
 
   SetUp(std::move(task_runner));

gin/public/isolate_holder.h

@@ -59,8 +59,7 @@ class GIN_EXPORT IsolateHolder {
                 AccessMode access_mode);
   IsolateHolder(scoped_refptr<base::SingleThreadTaskRunner> task_runner,
                 AccessMode access_mode,
-                AllowAtomicsWaitMode atomics_wait_mode,
-                v8::StartupData* startup_data);
+                AllowAtomicsWaitMode atomics_wait_mode);
 
   // This constructor is to create V8 snapshot for Blink.
   // Note this constructor calls isolate->Enter() internally.

gin/shell/gin_main.cc

@@ -71,7 +71,10 @@ int main(int argc, char** argv) {
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
   gin::V8Initializer::LoadV8Snapshot();
   gin::V8Initializer::LoadV8Natives();
-#endif
+#ifdef USE_V8_CONTEXT_SNAPSHOT
+  gin::V8Initializer::LoadV8ContextSnapshot();
+#endif  // USE_V8_CONTEXT_SNAPSHOT
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
   base::MessageLoop message_loop;
   base::TaskScheduler::CreateAndStartWithDefaultParams("gin");

gin/shell_runner_unittest.cc

@@ -32,6 +32,9 @@ TEST(RunnerTest, Run) {
   gin::V8Initializer::LoadV8Snapshot();
   gin::V8Initializer::LoadV8Natives();
 #endif
+#ifdef USE_V8_CONTEXT_SNAPSHOT
+  gin::V8Initializer::LoadV8ContextSnapshot();
+#endif
 
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::IsolateHolder::kStableV8Extras,

gin/test/file_runner.cc

@@ -63,7 +63,10 @@ void RunTestFromFile(const base::FilePath& path, FileRunnerDelegate* delegate,
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
   gin::V8Initializer::LoadV8Snapshot();
   gin::V8Initializer::LoadV8Natives();
-#endif
+#ifdef USE_V8_CONTEXT_SNAPSHOT
+  gin::V8Initializer::LoadV8ContextSnapshot();
+#endif  // USE_V8_CONTEXT_SNAPSHOT
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::IsolateHolder::kStableV8Extras,

gin/test/v8_test.cc

@@ -24,6 +24,10 @@ void V8Test::SetUp() {
   gin::V8Initializer::LoadV8Snapshot();
   gin::V8Initializer::LoadV8Natives();
 #endif
+#ifdef USE_V8_CONTEXT_SNAPSHOT
+  gin::V8Initializer::LoadV8ContextSnapshot();
+#endif
+
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kStrictMode,
                                  gin::IsolateHolder::kStableV8Extras,
                                  gin::ArrayBufferAllocator::SharedInstance());

gin/v8_initializer.cc

@@ -242,16 +242,22 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode,
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   v8::StartupData natives;
-  natives.data = reinterpret_cast<const char*>(g_mapped_natives->data());
-  natives.raw_size = static_cast<int>(g_mapped_natives->length());
+  GetMappedFileData(g_mapped_natives, &natives);
   v8::V8::SetNativesDataBlob(&natives);
 
+#if defined(USE_V8_CONTEXT_SNAPSHOT)
+  if (g_mapped_v8_context_snapshot) {
+    v8::StartupData snapshot{};
+    GetMappedFileData(g_mapped_v8_context_snapshot, &snapshot);
+    v8::V8::SetSnapshotDataBlob(&snapshot);
+  }
+#else
   if (g_mapped_snapshot) {
-    v8::StartupData snapshot;
-    snapshot.data = reinterpret_cast<const char*>(g_mapped_snapshot->data());
-    snapshot.raw_size = static_cast<int>(g_mapped_snapshot->length());
+    v8::StartupData snapshot{};
+    GetMappedFileData(g_mapped_snapshot, &snapshot);
     v8::V8::SetSnapshotDataBlob(&snapshot);
   }
+#endif  // USE_V8_CONTEXT_SNAPSHOT
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
   v8::V8::SetEntropySource(&GenerateEntropy);

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp

@@ -62,14 +62,10 @@ V8PerIsolateData::V8PerIsolateData(
     WebTaskRunner* task_runner,
     V8ContextSnapshotMode v8_context_snapshot_mode)
     : v8_context_snapshot_mode_(v8_context_snapshot_mode),
-      isolate_holder_(
-          task_runner,
-          gin::IsolateHolder::kSingleThread,
-          IsMainThread() ? gin::IsolateHolder::kDisallowAtomicsWait
-                         : gin::IsolateHolder::kAllowAtomicsWait,
-          v8_context_snapshot_mode_ == V8ContextSnapshotMode::kUseSnapshot
-              ? &startup_data_
-              : nullptr),
+      isolate_holder_(task_runner,
+                      gin::IsolateHolder::kSingleThread,
+                      IsMainThread() ? gin::IsolateHolder::kDisallowAtomicsWait
+                                     : gin::IsolateHolder::kAllowAtomicsWait),
       interface_template_map_for_v8_context_snapshot_(GetIsolate()),
       string_cache_(WTF::WrapUnique(new StringCache(GetIsolate()))),
       private_property_(V8PrivateProperty::Create()),
@@ -78,13 +74,6 @@ V8PerIsolateData::V8PerIsolateData(
       is_handling_recursion_level_error_(false),
       is_reporting_exception_(false),
       runtime_call_stats_(base::DefaultTickClock::GetInstance()) {
-  // If it fails to load the snapshot file, falls back to kDontUseSnapshot mode.
-  // TODO(peria): Remove this fallback routine.
-  if (v8_context_snapshot_mode_ == V8ContextSnapshotMode::kUseSnapshot &&
-      !startup_data_.data) {
-    v8_context_snapshot_mode_ = V8ContextSnapshotMode::kDontUseSnapshot;
-  }
-
   // FIXME: Remove once all v8::Isolate::GetCurrent() calls are gone.
   GetIsolate()->Enter();
   GetIsolate()->AddBeforeCallEnteredCallback(&BeforeCallEnteredCallback);