[cfe] Add a bit to Library to inticate if it's opted in for NNBD

Closes #37682.

Bug: http://dartbug.com/37682.
Change-Id: Ibe21cd0a1eac25a2883d2e2241d7476ca627edba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/114857
Commit-Queue: Dmitry Stefantsov <dmitryas@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Jens Johansen <jensj@google.com>

pkg/kernel/binary.md

@@ -143,7 +143,7 @@ type CanonicalName {
 
 type ComponentFile {
   UInt32 magic = 0x90ABCDEF;
-  UInt32 formatVersion = 31;
+  UInt32 formatVersion = 32;
   List<String> problemsAsJson; // Described in problems.md.
   Library[] libraries;
   UriSource sourceMap;
@@ -228,7 +228,7 @@ type Name {
 }
 
 type Library {
-  Byte flags (isExternal, isSynthetic);
+  Byte flags (isExternal, isSynthetic, isNonNullableOptedIn);
   UInt languageVersionMajor;
   UInt languageVersionMinor;
   CanonicalNameReference canonicalName;

pkg/kernel/lib/ast.dart

@@ -330,6 +330,7 @@ class Library extends NamedNode
 
   static const int ExternalFlag = 1 << 0;
   static const int SyntheticFlag = 1 << 1;
+  static const int NonNullableOptedInFlag = 1 << 2;
 
   int flags = 0;
 
@@ -354,6 +355,13 @@ class Library extends NamedNode
     flags = value ? (flags | SyntheticFlag) : (flags & ~SyntheticFlag);
   }
 
+  bool get isNonNullableOptedIn => (flags & NonNullableOptedInFlag) != 0;
+  void set isNonNullableOptedIn(bool value) {
+    flags = value
+        ? (flags | NonNullableOptedInFlag)
+        : (flags & ~NonNullableOptedInFlag);
+  }
+
   String name;
 
   /// Problems in this [Library] encoded as json objects.

pkg/kernel/lib/binary/tag.dart

@@ -146,7 +146,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h, pkg/kernel/binary.md.
-  static const int BinaryFormatVersion = 31;
+  static const int BinaryFormatVersion = 32;
 }
 
 abstract class ConstantTag {

runtime/vm/kernel_binary.h

@@ -20,7 +20,7 @@ static const uint32_t kMagicProgramFile = 0x90ABCDEFu;
 
 // Both version numbers are inclusive.
 static const uint32_t kMinSupportedKernelFormatVersion = 18;
-static const uint32_t kMaxSupportedKernelFormatVersion = 31;
+static const uint32_t kMaxSupportedKernelFormatVersion = 32;
 
 // Keep in sync with package:kernel/lib/binary/tag.dart
 #define KERNEL_TAG_LIST(V)                                                     \