Fix possible leaks in CanvasContext HintSessionWrapper

Ensure the mHintSessionFuture is accounted for correctly in the
destructor.

Bug: b/297230599
Test: manual
Change-Id: Idcbd0f2ba87290f090d693f0a64cb46fe8270b95
Merged-In: Idcbd0f2ba87290f090d693f0a64cb46fe8270b95
(cherry picked from commit ac620f64)

libs/hwui/renderthread/HintSessionWrapper.cpp

@@ -93,8 +93,13 @@ HintSessionWrapper::HintSessionWrapper(pid_t uiThreadId, pid_t renderThreadId)
         : mUiThreadId(uiThreadId), mRenderThreadId(renderThreadId) {}
 
 HintSessionWrapper::~HintSessionWrapper() {
+    if (mHintSessionFuture.valid()) {
+        mHintSession = mHintSessionFuture.get();
+    }
     if (mHintSession) {
         gAPH_closeSessionFn(mHintSession);
+        mSessionValid = true;
+        mHintSession = nullptr;
     }
 }