Convert `raw_hash_set` comments from imperative to indicative mood.

 https://google.github.io/styleguide/cppguide.html#Function_Comments

absl/container/internal/raw_hash_set.cc

@@ -107,21 +107,22 @@ FindInfo find_first_non_full_outofline(const CommonFields& common,
   return find_first_non_full(common, hash);
 }
 
-// Return address of the ith slot in slots where each slot occupies slot_size.
+// Returns the address of the ith slot in slots where each slot occupies
+// slot_size.
 static inline void* SlotAddress(void* slot_array, size_t slot,
                                 size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot_array) +
                                  (slot * slot_size));
 }
 
-// Return the address of the slot just after slot assuming each slot
-// has the specified size.
+// Returns the address of the slot just after slot assuming each slot has the
+// specified size.
 static inline void* NextSlot(void* slot, size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) + slot_size);
 }
 
-// Return the address of the slot just before slot assuming each slot
-// has the specified size.
+// Returns the address of the slot just before slot assuming each slot has the
+// specified size.
 static inline void* PrevSlot(void* slot, size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) - slot_size);
 }

absl/container/internal/raw_hash_set.h

@@ -376,12 +376,12 @@ class NonIterableBitMask {
     return static_cast<uint32_t>((bit_width(mask_) - 1) >> Shift);
   }
 
-  // Return the number of trailing zero *abstract* bits.
+  // Returns the number of trailing zero *abstract* bits.
   uint32_t TrailingZeros() const {
     return container_internal::TrailingZeros(mask_) >> Shift;
   }
 
-  // Return the number of leading zero *abstract* bits.
+  // Returns the number of leading zero *abstract* bits.
   uint32_t LeadingZeros() const {
     constexpr int total_significant_bits = SignificantBits << Shift;
     constexpr int extra_bits = sizeof(T) * 8 - total_significant_bits;
@@ -1361,7 +1361,7 @@ ABSL_ATTRIBUTE_NOINLINE void InitializeSlots(CommonFields& c, Alloc alloc) {
 struct PolicyFunctions {
   size_t slot_size;
 
-  // Return the hash of the pointed-to slot.
+  // Returns the hash of the pointed-to slot.
   size_t (*hash_slot)(void* set, void* slot);
 
   // Transfer the contents of src_slot to dst_slot.