Bug 991227 - Replace std::auto_ptr with nsAuto(Array)Ptr in LayerScope. r=dglastonbury

std::auto_ptr causes clang 3.5 build warnings because we shouldn't use
std::auto_ptr in C++ 11 anymore. auto_ptr is deprecated in clang 3.5.
Therefore I replaced all the std::auto_ptrs in LayerScope.cpp.
Note: nsAuto(Array)Ptr should use "new" operator in C++, instead of
moz_malloc() because the destructor of nsAuto(Array)Ptr will call
delete(delete []).
Bug 1015856 - Add gtest testcase for checking WebM aspect ratio. r=rillian
Bug 1024609 - Implemented RArgumentsLength reading the value stored on IonJSFrameLayout. r=nbp