Revert r192949 "Disable shader disk cache by default."

gpu/command_buffer/service/memory_program_cache.cc

Index: gpu/command_buffer/service/memory_program_cache.cc
diff --git a/gpu/command_buffer/service/memory_program_cache.cc b/gpu/command_buffer/service/memory_program_cache.cc
index 726c60d1488ed94904360e9629724f1268a8b276..d9d944db13c262a60db2583a7123c3998b0532e0 100644
--- a/gpu/command_buffer/service/memory_program_cache.cc
+++ b/gpu/command_buffer/service/memory_program_cache.cc
@@ -142,8 +142,8 @@ ProgramCache::ProgramLoadResult MemoryProgramCache::LoadLinkedProgram(
   shader_b->set_uniform_map(value->uniform_map_1);
 
   if (!shader_callback.is_null() &&
-      CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableGpuShaderDiskCache)) {
+      !CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableGpuShaderDiskCache)) {
     GpuProgramProto* proto = GpuProgramProto::default_instance().New();
     proto->set_sha(sha, kHashLength);
     proto->set_format(value->format);
@@ -212,8 +212,8 @@ void MemoryProgramCache::SaveLinkedProgram(
   }
 
   if (!shader_callback.is_null() &&
-      CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableGpuShaderDiskCache)) {
+      !CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableGpuShaderDiskCache)) {
     GpuProgramProto* proto = GpuProgramProto::default_instance().New();
     proto->set_sha(sha, kHashLength);
     proto->set_format(format);