[kernel] Don't use kernel ast nodes as keys

runtime/vm/kernel_binary.cc

Index: runtime/vm/kernel_binary.cc
diff --git a/runtime/vm/kernel_binary.cc b/runtime/vm/kernel_binary.cc
index d78612c410c2d0cad0710851a1d580e5e32bebe0..ff8e0faa7fa4dc50f09f381dbf816886128d5869 100644
--- a/runtime/vm/kernel_binary.cc
+++ b/runtime/vm/kernel_binary.cc
@@ -501,6 +501,8 @@ class Reader {
     return name;
   }
 
+  int64_t offset() { return offset_; }
+
  private:
   const uint8_t* buffer_;
   int64_t size_;
@@ -806,6 +808,7 @@ Field* Field::ReadFrom(Reader* reader) {
   Tag tag = reader->ReadTag();
   ASSERT(tag == kField);
 
+  kernelFileOffset_ = reader->offset();
   reader->ReadDefiningCanonicalNameReference(this);
   position_ = reader->ReadPosition(false);
   end_position_ = reader->ReadPosition(false);
@@ -1387,7 +1390,7 @@ AwaitExpression* AwaitExpression::ReadFrom(Reader* reader) {
 FunctionExpression* FunctionExpression::ReadFrom(Reader* reader) {
   TRACE_READ_OFFSET();
   VariableScope<ReaderHelper> parameters(reader->helper());
-  FunctionExpression* expr = new FunctionExpression();
+  FunctionExpression* expr = new FunctionExpression(reader->offset());
   expr->function_ = FunctionNode::ReadFrom(reader);
   return expr;
 }
@@ -1398,7 +1401,7 @@ Let* Let::ReadFrom(Reader* reader) {
   VariableScope<ReaderHelper> vars(reader->helper());
   PositionScope scope(reader);
 
-  Let* let = new Let();
+  Let* let = new Let(reader->offset());
   let->variable_ = VariableDeclaration::ReadFromImpl(reader);
   let->body_ = Expression::ReadFrom(reader);
   let->position_ = reader->min_position();
@@ -1478,7 +1481,7 @@ Block* Block::ReadFromImpl(Reader* reader) {
   PositionScope scope(reader);
 
   VariableScope<ReaderHelper> vars(reader->helper());
-  Block* block = new Block();
+  Block* block = new Block(reader->offset());
   block->statements().ReadFromStatic<Statement>(reader);
   block->position_ = reader->min_position();
   block->end_position_ = reader->max_position();
@@ -1544,7 +1547,7 @@ ForStatement* ForStatement::ReadFrom(Reader* reader) {
   VariableScope<ReaderHelper> vars(reader->helper());
   PositionScope scope(reader);
 
-  ForStatement* forstmt = new ForStatement();
+  ForStatement* forstmt = new ForStatement(reader->offset());
   forstmt->variables_.ReadFromStatic<VariableDeclarationImpl>(reader);
   forstmt->condition_ = reader->ReadOptional<Expression>();
   forstmt->updates_.ReadFromStatic<Expression>(reader);
@@ -1561,7 +1564,7 @@ ForInStatement* ForInStatement::ReadFrom(Reader* reader, bool is_async) {
   VariableScope<ReaderHelper> vars(reader->helper());
   PositionScope scope(reader);
 
-  ForInStatement* forinstmt = new ForInStatement();
+  ForInStatement* forinstmt = new ForInStatement(reader->offset());
   forinstmt->is_async_ = is_async;
   forinstmt->position_ = reader->ReadPosition();
   forinstmt->variable_ = VariableDeclaration::ReadFromImpl(reader);
@@ -1655,7 +1658,7 @@ Catch* Catch::ReadFrom(Reader* reader) {
   VariableScope<ReaderHelper> vars(reader->helper());
   PositionScope scope(reader);
 
-  Catch* c = new Catch();
+  Catch* c = new Catch(reader->offset());
   c->guard_ = DartType::ReadFrom(reader);
   c->exception_ =
       reader->ReadOptional<VariableDeclaration, VariableDeclarationImpl>();
@@ -1701,7 +1704,7 @@ VariableDeclaration* VariableDeclaration::ReadFromImpl(Reader* reader) {
   TRACE_READ_OFFSET();
   PositionScope scope(reader);
 
-  VariableDeclaration* decl = new VariableDeclaration();
+  VariableDeclaration* decl = new VariableDeclaration(reader->offset());
   decl->position_ = reader->ReadPosition();
   decl->equals_position_ = reader->ReadPosition();
   decl->flags_ = reader->ReadFlags();
@@ -1723,7 +1726,7 @@ VariableDeclaration* VariableDeclaration::ReadFromImpl(Reader* reader) {
 
 FunctionDeclaration* FunctionDeclaration::ReadFrom(Reader* reader) {
   TRACE_READ_OFFSET();
-  FunctionDeclaration* decl = new FunctionDeclaration();
+  FunctionDeclaration* decl = new FunctionDeclaration(reader->offset());
   decl->position_ = reader->ReadPosition();
   decl->variable_ = VariableDeclaration::ReadFromImpl(reader);
   VariableScope<ReaderHelper> parameters(reader->helper());
@@ -1905,7 +1908,7 @@ FunctionNode* FunctionNode::ReadFrom(Reader* reader) {
   TRACE_READ_OFFSET();
   TypeParameterScope<ReaderHelper> scope(reader->helper());
 
-  FunctionNode* function = new FunctionNode();
+  FunctionNode* function = new FunctionNode(reader->offset());
   function->position_ = reader->ReadPosition();
   function->end_position_ = reader->ReadPosition();
   function->async_marker_ =