[test] Add missing field definitions

Even static constant fields need to have definitions outside of the
class scope if a reference to them is passed.
This CL fixes link errors which occured on an independent CL
(https://crrev.com/c/730716).

Drive-by: Make the fields constexpr.

R=mstarzinger@chromium.org

Change-Id: Iff5dd1f3d41ddfba0c20531dbecd63c1d4c670e8
Reviewed-on: https://chromium-review.googlesource.com/732114Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48816}

test/cctest/compiler/test-code-generator.cc

@@ -257,20 +257,20 @@ class TestEnvironment : public HandleAndZoneScope {
  public:
   // These constants may be tuned to experiment with different environments.
 
-  static const int kGeneralRegisterCount = 4;
-  static const int kDoubleRegisterCount = 6;
+  static constexpr int kGeneralRegisterCount = 4;
+  static constexpr int kDoubleRegisterCount = 6;
 
-  static const int kTaggedSlotCount = 64;
-  static const int kFloat32SlotCount = 64;
-  static const int kFloat64SlotCount = 64;
-  static const int kStackParameterCount =
+  static constexpr int kTaggedSlotCount = 64;
+  static constexpr int kFloat32SlotCount = 64;
+  static constexpr int kFloat64SlotCount = 64;
+  static constexpr int kStackParameterCount =
       kTaggedSlotCount + kFloat32SlotCount + kFloat64SlotCount;
 
   // TODO(all): Test all types of constants (e.g. ExternalReference and
   // HeapObject).
-  static const int kSmiConstantCount = 4;
-  static const int kFloatConstantCount = 4;
-  static const int kDoubleConstantCount = 4;
+  static constexpr int kSmiConstantCount = 4;
+  static constexpr int kFloatConstantCount = 4;
+  static constexpr int kDoubleConstantCount = 4;
 
   TestEnvironment()
       : blocks_(main_zone()),
@@ -735,6 +735,17 @@ class TestEnvironment : public HandleAndZoneScope {
       allocated_slots_;
 };
 
+// static
+constexpr int TestEnvironment::kGeneralRegisterCount;
+constexpr int TestEnvironment::kDoubleRegisterCount;
+constexpr int TestEnvironment::kTaggedSlotCount;
+constexpr int TestEnvironment::kFloat32SlotCount;
+constexpr int TestEnvironment::kFloat64SlotCount;
+constexpr int TestEnvironment::kStackParameterCount;
+constexpr int TestEnvironment::kSmiConstantCount;
+constexpr int TestEnvironment::kFloatConstantCount;
+constexpr int TestEnvironment::kDoubleConstantCount;
+
 // Wrapper around the CodeGenerator. Code generated by this can only be called
 // using the given `TestEnvironment`.
 //