Rename constant::Constant to constant::Value.

This CL renames constant::Constant to constant::Value as it reads a bit
nicer.

Bug: tint:1718
Change-Id: I3489a271ebe229dabf98e7668bdaef4fec375534
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/114361
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
diff --git a/src/tint/sem/switch_statement.h b/src/tint/sem/switch_statement.h
index 4d18210..2476906 100644
--- a/src/tint/sem/switch_statement.h
+++ b/src/tint/sem/switch_statement.h
@@ -26,7 +26,7 @@
 class SwitchStatement;
 }  // namespace tint::ast
 namespace tint::constant {
-class Constant;
+class Value;
 }  // namespace tint::constant
 namespace tint::sem {
 class CaseStatement;
@@ -103,7 +103,7 @@
     /// Constructor
     /// @param decl the selector declaration
     /// @param val the case selector value, nullptr for a default selector
-    explicit CaseSelector(const ast::CaseSelector* decl, const constant::Constant* val = nullptr);
+    explicit CaseSelector(const ast::CaseSelector* decl, const constant::Value* val = nullptr);
 
     /// Destructor
     ~CaseSelector() override;
@@ -115,11 +115,11 @@
     const ast::CaseSelector* Declaration() const;
 
     /// @returns the selector constant value, or nullptr if this is the default selector
-    const constant::Constant* Value() const { return val_; }
+    const constant::Value* Value() const { return val_; }
 
   private:
     const ast::CaseSelector* const decl_;
-    const constant::Constant* const val_;
+    const constant::Value* const val_;
 };
 
 }  // namespace tint::sem