Use emulator options' memory_size to determine size of wasm buffer, allowing for

dynamically sized emulator memory sizes.

Note: This may not always work due to browser limitations.

src/browser/starter.js

@@ -243,7 +243,7 @@ function V86Starter(options)
     v86util.load_wasm(
         wasm_file,
         { "env": wasm_shared_funcs },
-        WASM_MEMORY_SIZE * 1024 * 1024,
+        options["memory_size"] + INTERNAL_MEM_SIZE,
         WASM_TABLE_SIZE,
         wm => {
             wm.instance.exports["__post_instantiate"]();

src/const.js

@@ -357,9 +357,9 @@ const P_DO_MANY_CYCLES = 2;
 
 var WASM_TABLE_SIZE = 0x10000;
 
-// XXX: This should not be fixed
-// in M
-const WASM_MEMORY_SIZE = 256;
+/** @const */
+// The space we need for misc internal state before the beginning of mem8; see global_pointers.h
+const INTERNAL_MEM_SIZE = 4096 + 0x100000 * 6;
 
 /** @const */
 const WASM_PAGE_SIZE = 64 * 1024;