[V8][asm.js] Adds support to global const variables.

test/cctest/asmjs/test-asm-typer.cc

 // Copyright 2016 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.
 
 #include <cstring>
 #include <functional>
 #include <iostream>
 #include <memory>
 
 #include "src/asmjs/asm-typer.h"
@@ skipping 487 matching lines @@
     }
   }
 }
 
 TEST(ErrorsInGlobalVariableDefinition) {
   const struct {
     const char* decl;
     const char* error_message;
   } kTests[] = {
       {"var v;", "Global variable missing initializer"},
-      {"var v = uninitialized;", "Invalid global variable initializer"},
+      {"var v = uninitialized;", "Undeclared identifier in global"},
       {"var v = 'use asm';", "type annotation - forbidden literal"},
       {"var v = 4294967296;", " - forbidden literal"},
-      {"var v = not_fround;", "Invalid global variable initializer"},
+      {"var v = not_fround;", "initialize a global must be a const"},

[bradnelson, 2016/10/19 21:52:07]

Add tests that hit:
Undeclared identifier in return statement
Identifier in return statement is not const
Undeclared identifier in variable declaration initializer
Identifier in variable declaration initializer must be const

Add something that covers (since that changed and we didn't catch:
Invalid variable initialization - it should be a literal, const, or
fround(literal).

[John, 2016/10/20 15:13:22]

Done.

       {"var v = not_fround(1);", "expected call fround(literal)"},
       {"var v = __fround__(1.0);", "expected call fround(literal)"},
       {"var v = fround(1.0, 1.0);", "expected call fround(literal)"},
       {"var v = fround(not_fround);", "literal argument for call to fround"},
       {"var v = stdlib.nan", "Invalid import"},
       {"var v = stdlib.Math.nan", "Invalid import"},
       {"var v = stdlib.Mathh.E", "Invalid import"},
       {"var v = stdlib.Math", "Invalid import"},
       {"var v = Stdlib.Math.E", "Invalid import"},
       {"var v = stdlib.Math.E[0]", "Invalid import"},
@@ skipping 1470 matching lines @@
   for (size_t ii = 0; ii < arraysize(kTests); ++ii) {
     if (!ValidationOf(Module(kTests[ii]))
              ->FailsWithMessage("Can't assign to immutable symbol")) {
       std::cerr << "Test:\n" << kTests[ii];
       CHECK(false);
     }
   }
 }
 
 }  // namespace