[cleanup] Fix/remove some incorrect/obsolete/trivial comments.

R=petermarshall@chromium.org

Bug: 
Change-Id: I4c14032aa1bd4fad39cf3db36556d53a529a52b3
Reviewed-on: https://chromium-review.googlesource.com/654865Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47916}

src/builtins/builtins-collections-gen.cc

@@ -611,7 +611,6 @@ void CollectionsBuiltinsAssembler::SameValueZeroHeapNumber(Node* key_float,
                                                            Label* if_not_same) {
   Label if_smi(this), if_keyisnan(this);
 
-  // If the candidate is not a string, the keys are not equal.
   GotoIf(TaggedIsSmi(candidate_key), &if_smi);
   GotoIfNot(IsHeapNumber(candidate_key), if_not_same);
 

src/code-stub-assembler.cc

@@ -8606,8 +8606,7 @@ Node* CodeStubAssembler::Equal(Node* lhs, Node* rhs, Node* context,
 
 Node* CodeStubAssembler::StrictEqual(Node* lhs, Node* rhs,
                                      Variable* var_type_feedback) {
-  // Here's pseudo-code for the algorithm below in case of kDontNegateResult
-  // mode; for kNegateResult mode we properly negate the result.
+  // Pseudo-code for the algorithm below:
   //
   // if (lhs == rhs) {
   //   if (lhs->IsHeapNumber()) return HeapNumber::cast(lhs)->value() != NaN;

src/objects.cc

@@ -2315,13 +2315,11 @@ Map* Map::GetPrototypeChainRootMap(Isolate* isolate) const {
 
 namespace {
 
-// Returns a non-SMI for JSObjects, but returns the hash code for simple
+// Returns a non-SMI for JSReceivers, but returns the hash code for simple
 // objects.  This avoids a double lookup in the cases where we know we will
-// add the hash to the JSObject if it does not already exist.
+// add the hash to the JSReceiver if it does not already exist.
 Object* GetSimpleHash(Object* object) {
   DisallowHeapAllocation no_gc;
-  // The object is either a Smi, a HeapNumber, a name, an odd-ball, a real JS
-  // object, or a Harmony proxy.
   if (object->IsSmi()) {
     uint32_t hash = ComputeIntegerHash(Smi::ToInt(object));
     return Smi::FromInt(hash & Smi::kMaxValue);