[[ Skia ]] Patch Skia to not use an unavailable C++11 feature

(cherry picked from commit 9f04864)

Author: livecodefraser

libskia/include/private/SkMutex.h

@@ -40,7 +40,11 @@ class SkBaseMutex {
 
 class SkMutex : public SkBaseMutex {
 public:
-    using SkBaseMutex::SkBaseMutex;
+    // [[ Patch ]] Work around a missing C++11 feature in older GCC versions
+    //using SkBaseMutex::SkBaseMutex;
+    constexpr SkMutex()
+        : SkBaseMutex() {}
+    
     ~SkMutex() { fSemaphore.cleanup(); }
 };
 

libskia/include/private/SkSemaphore.h

@@ -50,7 +50,11 @@ class SkBaseSemaphore {
 
 class SkSemaphore : public SkBaseSemaphore {
 public:
-    using SkBaseSemaphore::SkBaseSemaphore;
+    // [[ Patch ]] Work around a missing C++11 feature in older GCC versions
+    //using SkBaseSemaphore::SkBaseSemaphore;
+    constexpr SkSemaphore(int count = 0)
+        : SkBaseSemaphore(count) {}
+    
     ~SkSemaphore() { this->cleanup(); }
 };