Ignore remaining explicit warnings.

This CL ignores the remaining explicit warnings and enables the lint
flag.

Bug: dawn:1339
Change-Id: Idabc062c3d1a7ec563115dbfd600e80a908c856d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86873
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>

src/dawn/CPPLINT.cfg

@@ -1,5 +1,4 @@
 filter=-build/namespaces
 filter=-readability/casting
 filter=-readability/todo
-filter=-runtime/explicit
 filter=-runtime/indentation_namespace

src/dawn/common/RefBase.h

@@ -44,6 +44,7 @@ class RefBase {
     }
 
     // Constructors from nullptr.
+    // NOLINTNEXTLINE(runtime/explicit)
     constexpr RefBase(std::nullptr_t) : RefBase() {
     }
 
@@ -53,6 +54,7 @@ class RefBase {
     }
 
     // Constructors from a value T.
+    // NOLINTNEXTLINE(runtime/explicit)
     RefBase(T value) : mValue(value) {
         Reference(value);
     }

src/dawn/common/ityp_array.h

@@ -41,6 +41,7 @@ namespace ityp {
         constexpr array() = default;
 
         template <typename... Values>
+        // NOLINTNEXTLINE(runtime/explicit)
         constexpr array(Values&&... values) : Base{std::forward<Values>(values)...} {
         }
 

src/dawn/common/ityp_bitset.h

@@ -39,6 +39,7 @@ namespace ityp {
         constexpr bitset() noexcept : Base() {
         }
 
+        // NOLINTNEXTLINE(runtime/explicit)
         constexpr bitset(uint64_t value) noexcept : Base(value) {
         }