CMake: Compile in OSMesa on Linux, if found.

cmake/CMakeLists.txt

Index: cmake/CMakeLists.txt
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 36a6d1ecf3ca947363c8197efebd4a2e5e82a64c..50e45d2226d43cbce693eb6c8205fde9bc378027 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -100,7 +100,6 @@ remove_srcs(
     ../src/gpu/gl/command_buffer/*
     ../src/gpu/gl/egl/*
     ../src/gpu/gl/iOS/*
-    ../src/gpu/gl/mesa/*
     ../src/opts/SkBitmapProcState_opts_none.cpp
     ../src/opts/SkBlitMask_opts_none.cpp
     ../src/opts/SkBlitRow_opts_none.cpp
@@ -199,6 +198,13 @@ endif()
 find_package(OpenGL REQUIRED)
 list (APPEND libs  ${OPENGL_LIBRARIES})
 
+if (UNIX AND NOT APPLE AND EXISTS "/usr/include/GL/osmesa.h")
+    set(SK_MESA 1)
+    list (APPEND libs "OSMesa")
+else()
+    remove_srcs(../src/gpu/gl/mesa/*)
+endif()
+
 # This is our main output, libskia.so.
 # We mostly build an .so here because it helps test we've linked everything,
 # not so much that we think Skia is a good candidate to ship as a shared library.
@@ -208,6 +214,12 @@ target_compile_definitions(skia
     PUBLIC
     PRIVATE -DSKIA_DLL)
 
+if (SK_MESA)
+    target_compile_definitions(skia

[mtklein, 2015/09/21 15:51:56]

Even if this works, I'd prefer it if you switch things over to appending to
${public_defines} and ${private_defines}, and call target_compile_definitions
exactly once.

+        PUBLIC  -DSK_MESA
+        PRIVATE -DSK_MESA)
+endif()
+
 target_include_directories(skia
     PUBLIC  ${public_includes}
     PRIVATE ${private_includes})