[wasm] memory size is an uint32_t, not a size_t.

BUG=

Review-Url: https://codereview.chromium.org/2077623002
Cr-Commit-Position: refs/heads/master@{#37044}

src/compiler/wasm-compiler.cc

@@ -2578,7 +2578,7 @@ void WasmGraphBuilder::BoundsCheckMem(MachineType memtype, Node* index,
                                       uint32_t offset,
                                       wasm::WasmCodePosition position) {
   DCHECK(module_ && module_->instance);
-  size_t size = module_->instance->mem_size;
+  uint32_t size = module_->instance->mem_size;
   byte memsize = wasm::WasmOpcodes::MemSize(memtype);
 
   // Check against the effective size.

src/wasm/wasm-module.h

@@ -225,7 +225,7 @@ struct WasmModuleInstance {
   std::vector<Handle<Code>> import_code;    // code objects for each import.
   // -- raw memory ------------------------------------------------------------
   byte* mem_start;  // start of linear memory.
-  size_t mem_size;  // size of the linear memory.
+  uint32_t mem_size;  // size of the linear memory.
   // -- raw globals -----------------------------------------------------------
   byte* globals_start;  // start of the globals area.
 

test/cctest/wasm/wasm-run-utils.h

@@ -96,7 +96,7 @@ class TestingModule : public ModuleEnv {
     if (interpreter_) delete interpreter_;
   }
 
-  byte* AddMemory(size_t size) {
+  byte* AddMemory(uint32_t size) {
     CHECK_NULL(instance->mem_start);
     CHECK_EQ(0, instance->mem_size);
     instance->mem_start = reinterpret_cast<byte*>(malloc(size));
@@ -107,7 +107,7 @@ class TestingModule : public ModuleEnv {
   }
 
   template <typename T>
-  T* AddMemoryElems(size_t count) {
+  T* AddMemoryElems(uint32_t count) {
     AddMemory(count * sizeof(T));
     return raw_mem_start<T>();
   }