Fix APIGetInstance() didn't increase external ref.

InstanceBase has two seperate ref counts: external & internal.
When we return it to the external user, we need to increase external
ref count as well.

Bug: chromium:1429835
Change-Id: I4b585d04149180418bd620e6e4d86522e033b64e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/126080
Commit-Queue: Quyen Le <lehoangquyen@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/dawn/native/Adapter.cpp

@@ -86,7 +86,7 @@ MaybeError AdapterBase::Initialize() {
 InstanceBase* AdapterBase::APIGetInstance() const {
     auto instance = GetInstance();
     ASSERT(instance != nullptr);
-    instance->Reference();
+    instance->APIReference();
     return instance;
 }
 

src/dawn/tests/end2end/AdapterDiscoveryTests.cpp

@@ -335,4 +335,21 @@ TEST_F(AdapterCreationTest, PreferLowPower) {
     }
 }
 
+// Test that GetInstance() returns the correct Instance.
+TEST_F(AdapterCreationTest, GetInstance) {
+    wgpu::RequestAdapterOptions options = {};
+
+    MockCallback<WGPURequestAdapterCallback> cb;
+
+    WGPUAdapter cAdapter = nullptr;
+    EXPECT_CALL(cb, Call(WGPURequestAdapterStatus_Success, _, nullptr, this))
+        .WillOnce(SaveArg<1>(&cAdapter));
+    instance.RequestAdapter(&options, cb.Callback(), cb.MakeUserdata(this));
+
+    wgpu::Adapter adapter = wgpu::Adapter::Acquire(cAdapter);
+    EXPECT_EQ(adapter != nullptr, anyAdapterAvailable);
+
+    EXPECT_EQ(adapter.GetInstance().Get(), instance.Get());
+}
+
 }  // anonymous namespace