tint: Add Initialize() / Shutdown() public APIs

Have Initialize() bind the Program printer - which is helpful for debugging.
Call these from dawn/node.

This allows dawn/node to print programs when things go wrong.

Change-Id: I32d8805381d2939e82dc6ea383b9860fbb5fb69e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/107684
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

include/tint/tint.h

@@ -15,6 +15,9 @@
 #ifndef INCLUDE_TINT_TINT_H_
 #define INCLUDE_TINT_TINT_H_
 
+// Guard for accidental includes to private headers
+#define CURRENTLY_IN_TINT_PUBLIC_HEADER
+
 // TODO(tint:88): When implementing support for an install target, all of these
 //                headers will need to be moved to include/tint/.
 
@@ -64,4 +67,16 @@
 #include "src/tint/writer/glsl/generator.h"
 #endif  // TINT_BUILD_GLSL_WRITER
 
+namespace tint {
+
+/// Initialize initializes the Tint library. Call before using the Tint API.
+void Initialize();
+
+/// Shutdown uninitializes the Tint library. Call after using the Tint API.
+void Shutdown();
+
+}  // namespace tint
+
+#undef CURRENTLY_IN_TINT_PUBLIC_HEADER
+
 #endif  // INCLUDE_TINT_TINT_H_