Bug 1170045 - part 0 - modify TestSegmentedVectors to use explicitly-updated counts; r=erahm

The scheme in TestSegmentedVectors to use manually-annotated points and
magic numbers corresponding to those annotations works OK for small
numbers of operations.  But for testing bulk push and pop, we're going
to be doing many more operations, so let's move to recording explicitly
in code the operations we expect to see, and checking those instead.

mfbt/tests/TestSegmentedVector.cpp

@@ -120,28 +120,43 @@ struct NonPOD
 // destruct those elements.
 void TestConstructorsAndDestructors()
 {
+  size_t defaultCtorCalls = 0;
+  size_t explicitCtorCalls = 0;
+  size_t copyCtorCalls = 0;
+  size_t moveCtorCalls = 0;
+  size_t dtorCalls = 0;
+
   {
     // A SegmentedVector with a non-POD element type.
     NonPOD x(1);                          // explicit constructor called
+    explicitCtorCalls++;
     SegmentedVector<NonPOD, 64, InfallibleAllocPolicy> v;
                                           // default constructor called 0 times
     MOZ_RELEASE_ASSERT(v.IsEmpty());
     gDummy = v.Append(x);                 // copy constructor called
+    copyCtorCalls++;
     NonPOD y(1);                          // explicit constructor called
+    explicitCtorCalls++;
     gDummy = v.Append(mozilla::Move(y));  // move constructor called
+    moveCtorCalls++;
     NonPOD z(1);                          // explicit constructor called
+    explicitCtorCalls++;
     v.InfallibleAppend(mozilla::Move(z)); // move constructor called
+    moveCtorCalls++;
     v.PopLast();                          // destructor called 1 time
-    MOZ_RELEASE_ASSERT(gNumDtors == 1);
+    dtorCalls++;
+    MOZ_RELEASE_ASSERT(gNumDtors == dtorCalls);
     v.Clear();                            // destructor called 2 times
+    dtorCalls += 2;
 
-    MOZ_RELEASE_ASSERT(gNumDefaultCtors  == 0);
-    MOZ_RELEASE_ASSERT(gNumExplicitCtors == 3);
-    MOZ_RELEASE_ASSERT(gNumCopyCtors     == 1);
-    MOZ_RELEASE_ASSERT(gNumMoveCtors     == 2);
-    MOZ_RELEASE_ASSERT(gNumDtors         == 3);
+    MOZ_RELEASE_ASSERT(gNumDefaultCtors  == defaultCtorCalls);
+    MOZ_RELEASE_ASSERT(gNumExplicitCtors == explicitCtorCalls);
+    MOZ_RELEASE_ASSERT(gNumCopyCtors     == copyCtorCalls);
+    MOZ_RELEASE_ASSERT(gNumMoveCtors     == moveCtorCalls);
+    MOZ_RELEASE_ASSERT(gNumDtors         == dtorCalls);
   }                                       // destructor called for x, y, z
-  MOZ_RELEASE_ASSERT(gNumDtors == 6);
+  dtorCalls += 3;
+  MOZ_RELEASE_ASSERT(gNumDtors == dtorCalls);
 }
 
 struct A { int mX; int mY; };