help msvc -analyzer out wrt SkASSERT

Change-Id: I32387c80273d0bc080e47a1d9ccf7454a4a3d79a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167518
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

external/skia/UnpackedTarball_skia.mk

@@ -42,6 +42,7 @@ skia_patches := \
     incomplete-type-SkImageGenerator.patch.1 \
     0001-AvoidCombiningExtrememelyLargeMeshes.patch.1 \
     sort-comparison-assumption.patch.0 \
+    help-msvc-analyzer.patch \
 
 $(eval $(call gb_UnpackedTarball_set_patchlevel,skia,1))
 

external/skia/help-msvc-analyzer.patch

@@ -0,0 +1,25 @@
+--- skia/include/private/base/SkAssert.h.orig
++++ skia/include/private/base/SkAssert.h
+@@ -43,6 +43,13 @@
+     } while (false)
+ #endif
+ 
++// when building with msvc and only when using these headers outside the skia build
++#if defined(_MSC_VER) && !defined(SKIA_IMPLEMENTATION)
++#    define SkANALYSIS_ASSUME(condition) __analysis_assume(condition)
++#else
++#    define SkANALYSIS_ASSUME(condition) static_cast<void>(0)
++#endif
++
+ // SkASSERT, SkASSERTF and SkASSERT_RELEASE can be used as stand alone assertion expressions, e.g.
+ //    uint32_t foo(int x) {
+ //        SkASSERT(x > 4);
+@@ -54,7 +60,7 @@
+ //               x - 4;
+ //    }
+ #define SkASSERT_RELEASE(cond) \
+-        static_cast<void>( (cond) ? (void)0 : []{ SK_ABORT("assert(%s)", #cond); }() )
++        static_cast<void>( (cond) ? (void)0 : [&]{ SK_ABORT("assert(%s)", #cond); SkANALYSIS_ASSUME(cond); }() )
+ 
+ #if defined(SK_DEBUG)
+     #define SkASSERT(cond) SkASSERT_RELEASE(cond)