[wasm] Add support for import section.

src/wasm/ast-decoder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_AST_DECODER_H_
 #define V8_WASM_AST_DECODER_H_
 
 #include "src/signature.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/wasm-opcodes.h"
@@ skipping 114 matching lines @@
 struct FunctionIndexOperand {
   uint32_t index;
   FunctionSig* sig;
   int length;
   inline FunctionIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "function index");
     sig = nullptr;
   }
 };
 
+struct ImportIndexOperand {
+  uint32_t index;
+  FunctionSig* sig;
+  int length;
+  inline ImportIndexOperand(Decoder* decoder, const byte* pc) {
+    index = decoder->checked_read_u32v(pc, 1, &length, "import index");
+    sig = nullptr;
+  }
+};
+
 struct TableSwitchOperand {
   uint32_t case_count;
   uint32_t table_count;
   const byte* table;
   int length;
   inline TableSwitchOperand(Decoder* decoder, const byte* pc) {
     case_count = decoder->checked_read_u16(pc, 1, "expected #cases");
     table_count = decoder->checked_read_u16(pc, 3, "expected #entries");
     length = 4 + table_count * 2;
 
@@ skipping 119 matching lines @@
 // Computes the length of the opcode at the given address.
 int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
 int OpcodeArity(FunctionEnv* env, const byte* pc, const byte* end);
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_AST_DECODER_H_