Revert "[VM] Adds Future.then and Future.catchError stack unwinding."

This reverts commit 8f2c47f.

Reason for revert: We suspect this is causing VM crashes: http://b/177506826

Original change's description:
> [VM] Adds Future.then and Future.catchError stack unwinding.
>
> TEST=Various 'causal' tests updated below.
>
> Bug: #40815, #37953
> Change-Id: I1420d6163ac2e3b22e0971f7b0ad516895dded70
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/176662
> Commit-Queue: Clement Skau <[email protected]>
> Reviewed-by: Vyacheslav Egorov <[email protected]>

[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: #40815
Bug: #37953
Change-Id: I870f0202f43588f71a5d2b0f82338978b5a5dda9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/178998
Reviewed-by: Michal Terepeta <[email protected]>
Reviewed-by: Vyacheslav Egorov <[email protected]>
Commit-Queue: Michal Terepeta <[email protected]>

Author: michalt

pkg/vm_service/test/get_stack_test.dart

@@ -52,12 +52,11 @@ final tests = <IsolateTest>[
   // Before the first await.
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_A),
-  // At LINE_A we're still running sync. so no asyncCausalFrames.
   (VmService service, IsolateRef isolateRef) async {
     final result = await service.getStack(isolateRef.id);
 
     expect(result.frames, hasLength(16));
-    expect(result.asyncCausalFrames, isNull);
+    expect(result.asyncCausalFrames, hasLength(16));
     expect(result.awaiterFrames, hasLength(16));
 
     expectFrames(result.frames, [
@@ -74,6 +73,20 @@ final tests = <IsolateTest>[
       [equals('Regular'), endsWith(' testMain')],
     ]);
 
+    expectFrames(result.asyncCausalFrames, [
+      [equals('Regular'), endsWith(' func10')],
+      [equals('Regular'), endsWith(' func9')],
+      [equals('Regular'), endsWith(' func8')],
+      [equals('Regular'), endsWith(' func7')],
+      [equals('Regular'), endsWith(' func6')],
+      [equals('Regular'), endsWith(' func5')],
+      [equals('Regular'), endsWith(' func4')],
+      [equals('Regular'), endsWith(' func3')],
+      [equals('Regular'), endsWith(' func2')],
+      [equals('Regular'), endsWith(' func1')],
+      [equals('Regular'), endsWith(' testMain')],
+    ]);
+
     expectFrames(result.awaiterFrames, [
       [equals('AsyncActivation'), endsWith(' func10')],
       [equals('AsyncActivation'), endsWith(' func9')],
@@ -88,10 +101,10 @@ final tests = <IsolateTest>[
       [equals('AsyncActivation'), endsWith(' testMain')],
     ]);
   },
+  // After resuming the continuation - i.e. running async.
   resumeIsolate,
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_B),
-  // After resuming the continuation - i.e. running async.
   (VmService service, IsolateRef isolateRef) async {
     final result = await service.getStack(isolateRef.id);
 

runtime/observatory/tests/service/causal_async_stack_presence_test.dart

@@ -11,16 +11,15 @@ import 'service_test_common.dart';
 import 'test_helper.dart';
 
 const LINE_C = 19;
-const LINE_A = 25;
-const LINE_B = 31;
+const LINE_A = 24;
+const LINE_B = 30;
 
 foobar() {
   debugger();
   print('foobar'); // LINE_C.
 }
 
 helper() async {
-  await 0; // Yield. The rest will run async.
   debugger();
   print('helper'); // LINE_A.
   foobar();
@@ -37,15 +36,14 @@ var tests = <IsolateTest>[
   (Isolate isolate) async {
     ServiceMap stack = await isolate.getStack();
     // No causal frames because we are in a completely synchronous stack.
-    // Async function hasn't yielded yet.
     expect(stack['asyncCausalFrames'], isNull);
   },
   resumeIsolate,
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_A),
   (Isolate isolate) async {
     ServiceMap stack = await isolate.getStack();
-    // Async function has yielded once, so it's now running async.
+    // Has causal frames (we are inside an async function)
     expect(stack['asyncCausalFrames'], isNotNull);
   },
   resumeIsolate,

runtime/observatory/tests/service/causal_async_star_stack_presence_test.dart

@@ -39,7 +39,7 @@ var tests = <IsolateTest>[
   (Isolate isolate) async {
     ServiceMap stack = await isolate.getStack();
     // No causal frames because we are in a completely synchronous stack.
-    expect(stack['asyncCausalFrames'], isNull);
+    expect(stack['asyncCausalFrames'], isNotNull);
   },
   resumeIsolate,
   hasStoppedAtBreakpoint,

runtime/observatory_2/tests/service_2/causal_async_stack_presence_test.dart

@@ -11,16 +11,15 @@ import 'service_test_common.dart';
 import 'test_helper.dart';
 
 const LINE_C = 19;
-const LINE_A = 25;
-const LINE_B = 31;
+const LINE_A = 24;
+const LINE_B = 30;
 
 foobar() {
   debugger();
   print('foobar'); // LINE_C.
 }
 
 helper() async {
-  await 0; // Yield. The rest will run async.
   debugger();
   print('helper'); // LINE_A.
   foobar();

runtime/observatory_2/tests/service_2/causal_async_star_stack_presence_test.dart

@@ -39,7 +39,7 @@ var tests = <IsolateTest>[
   (Isolate isolate) async {
     ServiceMap stack = await isolate.getStack();
     // No causal frames because we are in a completely synchronous stack.
-    expect(stack['asyncCausalFrames'], isNull);
+    expect(stack['asyncCausalFrames'], isNotNull);
   },
   resumeIsolate,
   hasStoppedAtBreakpoint,