Add initializer support to FatVector

Added constructor to FatVector to support C++ initializer
list usage

Test: Added tests to CanvasOpTest
Change-Id: If28066af1b1d747bab4e01b4d6a563412a11e7ec
diff --git a/libs/ui/include/ui/FatVector.h b/libs/ui/include/ui/FatVector.h
index 25fe3a0..cb61e6a 100644
--- a/libs/ui/include/ui/FatVector.h
+++ b/libs/ui/include/ui/FatVector.h
@@ -82,6 +82,12 @@
         this->reserve(SIZE);
     }
 
+    FatVector(std::initializer_list<T> init)
+          : std::vector<T, InlineStdAllocator<T, SIZE>>(init,
+                                                        InlineStdAllocator<T, SIZE>(mAllocation)) {
+        this->reserve(SIZE);
+    }
+
     explicit FatVector(size_t capacity) : FatVector() { this->resize(capacity); }
 
 private: