[wasm] Remove dangerous {WasmCompiledModule} accessors.

Note that {nullptr} is a dangerous sentinel value in V8's object model
because it can be interpreted as Smi(0) and hence will turn into a
completely different type than the declared return type at runtime.

R=ahaas@chromium.org
BUG=v8:7509

Change-Id: I89cffa1160a3bf6853f91c04fb90c74ad08888a3
Reviewed-on: https://chromium-review.googlesource.com/948907Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51757}

src/wasm/wasm-objects-inl.h

@@ -94,12 +94,6 @@ OPTIONAL_ACCESSORS(WasmDebugInfo, c_wasm_entry_map, Managed<wasm::SignatureMap>,
 #undef OPTIONAL_ACCESSORS
 
 #define WCM_OBJECT_OR_WEAK(TYPE, NAME, OFFSET, TYPE_CHECK)   \
-  TYPE* WasmCompiledModule::maybe_##NAME() const {           \
-    Object* value = READ_FIELD(this, OFFSET);                \
-    if (!(TYPE_CHECK)) return nullptr;                       \
-    return TYPE::cast(value);                                \
-  }                                                          \
-                                                             \
   bool WasmCompiledModule::has_##NAME() const {              \
     Object* value = READ_FIELD(this, OFFSET);                \
     return TYPE_CHECK;                                       \

src/wasm/wasm-objects.h

@@ -453,7 +453,6 @@ class WasmCompiledModule : public Struct {
 
 #define WCM_OBJECT_OR_WEAK(TYPE, NAME, SETTER_MODIFIER) \
  public:                                                \
-  inline TYPE* maybe_##NAME() const;                    \
   inline TYPE* NAME() const;                            \
   inline bool has_##NAME() const;                       \
   inline void reset_##NAME();                           \