SkiaVkRenderEngine: Do not cache textures with protected contexts

`SkiaRenderEngine::mTextureCache` is not used with protected contexts
with the SkiaVk back-end.  This avoids crashed caused by using a
VkImage with a VkDevice that it wasn't created with.

Test: Face unlock training
Bug: 271907068
Bug: 264475961
Bug: 267295152
Change-Id: I1296539677ae63be63614ab2464dbb55b32276cd
diff --git a/libs/renderengine/skia/SkiaRenderEngine.h b/libs/renderengine/skia/SkiaRenderEngine.h
index dd6646b..e4406b4 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.h
+++ b/libs/renderengine/skia/SkiaRenderEngine.h
@@ -133,6 +133,8 @@
     void unmapExternalTextureBuffer(sp<GraphicBuffer>&& buffer) override final;
     bool canSkipPostRenderCleanup() const override final;
 
+    std::shared_ptr<AutoBackendTexture::LocalRef> getOrCreateBackendTexture(
+            const sp<GraphicBuffer>& buffer, bool isOutputBuffer) REQUIRES(mRenderingMutex);
     void initCanvas(SkCanvas* canvas, const DisplaySettings& display);
     void drawShadow(SkCanvas* canvas, const SkRRect& casterRRect,
                     const ShadowSettings& shadowSettings);
@@ -167,7 +169,9 @@
     // Number of external holders of ExternalTexture references, per GraphicBuffer ID.
     std::unordered_map<GraphicBufferId, int32_t> mGraphicBufferExternalRefs
             GUARDED_BY(mRenderingMutex);
-    // Cache of GL textures that we'll store per GraphicBuffer ID, shared between GPU contexts.
+    // For GL, this cache is shared between protected and unprotected contexts. For Vulkan, it is
+    // only used for the unprotected context, because Vulkan does not allow sharing between
+    // contexts, and protected is less common.
     std::unordered_map<GraphicBufferId, std::shared_ptr<AutoBackendTexture::LocalRef>> mTextureCache
             GUARDED_BY(mRenderingMutex);
     std::unordered_map<shaders::LinearEffect, sk_sp<SkRuntimeEffect>, shaders::LinearEffectHasher>