Reland "[chromium-style] Adding constructors and destructors."

This reverts commit 63cea3f8c0.

...except it skips adding the the constructor/destructor/copy
definitions for dawn::native::Format. Adding them triggers "constexpr
variable cannot have non-literal type" (or "declaration requires a
global constructor" if it's not marked constexpr), unless they're
explicitly marked as =default in the header - which just triggers a
different chromium-style warning, so there's no point.

A better solution to the chromium-style warning on Format may be to just
make the class physically smaller:
https://www.chromium.org/developers/coding-style/chromium-style-checker-errors/#constructordestructor-errors

Bug: dawn:1405
Change-Id: Ied6e9d0abff6bf1330131a40c6583bab18888b67
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/90303
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>

include/dawn/native/DawnNative.h

@@ -39,6 +39,9 @@ class AdapterBase;
 // An optional parameter of Adapter::CreateDevice() to send additional information when creating
 // a Device. For example, we can use it to enable a workaround, optimization or feature.
 struct DAWN_NATIVE_EXPORT DawnDeviceDescriptor {
+    DawnDeviceDescriptor();
+    ~DawnDeviceDescriptor();
+
     std::vector<const char*> requiredFeatures;
     std::vector<const char*> forceEnabledToggles;
     std::vector<const char*> forceDisabledToggles;