Fix starting isolate directly from CoreJIT snapshot. (flutter/engine#5798)

engine/src/flutter/runtime/dart_isolate.cc

@@ -257,10 +257,6 @@ bool DartIsolate::PrepareForRunningFromPrecompiledCode() {
     return false;
   }
 
-  if (!DartVM::IsRunningPrecompiledCode()) {
-    return false;
-  }
-
   tonic::DartState::Scope scope(this);
 
   if (Dart_IsNull(Dart_RootLibrary())) {
@@ -342,9 +338,8 @@ bool DartIsolate::PrepareForRunningFromSnapshot(
 
   tonic::DartState::Scope scope(this);
 
-  if (!Dart_IsNull(Dart_RootLibrary())) {
-    return false;
-  }
+  // Use root library provided by kernel in favor of one provided by snapshot.
+  Dart_SetRootLibrary(Dart_Null());
 
   if (!LoadSnapshot(mapping, last_piece)) {
     return false;

engine/src/flutter/shell/common/isolate_configuration.cc

@@ -31,20 +31,17 @@ bool IsolateConfiguration::PrepareIsolate(
   return DoPrepareIsolate(*isolate);
 }
 
-class PrecompiledIsolateConfiguration final : public IsolateConfiguration {
+class AppSnapshotIsolateConfiguration final : public IsolateConfiguration {
  public:
-  PrecompiledIsolateConfiguration() = default;
+  AppSnapshotIsolateConfiguration() = default;
 
   // |shell::IsolateConfiguration|
   bool DoPrepareIsolate(blink::DartIsolate& isolate) override {
-    if (!blink::DartVM::IsRunningPrecompiledCode()) {
-      return false;
-    }
     return isolate.PrepareForRunningFromPrecompiledCode();
   }
 
  private:
-  FXL_DISALLOW_COPY_AND_ASSIGN(PrecompiledIsolateConfiguration);
+  FXL_DISALLOW_COPY_AND_ASSIGN(AppSnapshotIsolateConfiguration);
 };
 
 class SnapshotIsolateConfiguration : public IsolateConfiguration {
@@ -122,7 +119,7 @@ std::unique_ptr<IsolateConfiguration> IsolateConfiguration::InferFromSettings(
     fml::RefPtr<blink::AssetManager> asset_manager) {
   // Running in AOT mode.
   if (blink::DartVM::IsRunningPrecompiledCode()) {
-    return CreateForPrecompiledCode();
+    return CreateForAppSnapshot();
   }
 
   // Run from sources.
@@ -193,8 +190,8 @@ std::unique_ptr<IsolateConfiguration> IsolateConfiguration::InferFromSettings(
 }
 
 std::unique_ptr<IsolateConfiguration>
-IsolateConfiguration::CreateForPrecompiledCode() {
-  return std::make_unique<PrecompiledIsolateConfiguration>();
+IsolateConfiguration::CreateForAppSnapshot() {
+  return std::make_unique<AppSnapshotIsolateConfiguration>();
 }
 
 std::unique_ptr<IsolateConfiguration> IsolateConfiguration::CreateForSnapshot(

engine/src/flutter/shell/common/isolate_configuration.h

@@ -24,7 +24,7 @@ class IsolateConfiguration {
       const blink::Settings& settings,
       fml::RefPtr<blink::AssetManager> asset_manager);
 
-  static std::unique_ptr<IsolateConfiguration> CreateForPrecompiledCode();
+  static std::unique_ptr<IsolateConfiguration> CreateForAppSnapshot();
 
   static std::unique_ptr<IsolateConfiguration> CreateForSnapshot(
       std::unique_ptr<fml::Mapping> snapshot);

engine/src/flutter/shell/platform/android/platform_view_android_jni.cc

@@ -178,7 +178,7 @@ static void SurfaceDestroyed(JNIEnv* env, jobject jcaller, jlong shell_holder) {
 std::unique_ptr<IsolateConfiguration> CreateIsolateConfiguration(
     const blink::AssetManager& asset_manager) {
   if (blink::DartVM::IsRunningPrecompiledCode()) {
-    return IsolateConfiguration::CreateForPrecompiledCode();
+    return IsolateConfiguration::CreateForAppSnapshot();
   }
 
   const auto configuration_from_blob =
@@ -200,7 +200,8 @@ std::unique_ptr<IsolateConfiguration> CreateIsolateConfiguration(
     return script;
   }
 
-  return nullptr;
+  // This happens when starting isolate directly from CoreJIT snapshot.
+  return IsolateConfiguration::CreateForAppSnapshot();
 }
 
 static void RunBundleAndSnapshot(