Update from https://crrev.com/315085

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 4bf16e38e7e06e73e1e1dc5586ad9590b098fc3e..1e8e11b870bff6dfeb6315a4992638a3c7d4f0a6 100644
--- a/gpu/command_buffer/service/memory_program_cache.cc
+++ b/gpu/command_buffer/service/memory_program_cache.cc
@@ -180,12 +180,12 @@ ProgramCache::ProgramLoadResult MemoryProgramCache::LoadLinkedProgram(
     const ShaderCacheCallback& shader_callback) {
   char a_sha[kHashLength];
   char b_sha[kHashLength];
-  DCHECK(shader_a && !shader_a->signature_source().empty() &&
-         shader_b && !shader_b->signature_source().empty());
+  DCHECK(shader_a && !shader_a->last_compiled_source().empty() &&
+         shader_b && !shader_b->last_compiled_source().empty());
   ComputeShaderHash(
-      shader_a->signature_source(), translator_a, a_sha);
+      shader_a->last_compiled_source(), translator_a, a_sha);
   ComputeShaderHash(
-      shader_b->signature_source(), translator_b, b_sha);
+      shader_b->last_compiled_source(), translator_b, b_sha);
 
   char sha[kHashLength];
   ComputeProgramHash(a_sha,
@@ -256,12 +256,12 @@ void MemoryProgramCache::SaveLinkedProgram(
 
   char a_sha[kHashLength];
   char b_sha[kHashLength];
-  DCHECK(shader_a && !shader_a->signature_source().empty() &&
-         shader_b && !shader_b->signature_source().empty());
+  DCHECK(shader_a && !shader_a->last_compiled_source().empty() &&
+         shader_b && !shader_b->last_compiled_source().empty());
   ComputeShaderHash(
-      shader_a->signature_source(), translator_a, a_sha);
+      shader_a->last_compiled_source(), translator_a, a_sha);
   ComputeShaderHash(
-      shader_b->signature_source(), translator_b, b_sha);
+      shader_b->last_compiled_source(), translator_b, b_sha);
 
   char sha[kHashLength];
   ComputeProgramHash(a_sha,