Added null check for shader source when compiling, and fixed re-caching behavior to spec

gpu/command_buffer/service/memory_program_cache_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/memory_program_cache.h"
 
 #include "gpu/command_buffer/common/gl_mock.h"
 #include "gpu/command_buffer/common/gles2_cmd_format.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/command_buffer/service/shader_translator.h"
@@ skipping 20 matching lines @@
                         const char* binary)
       : length_(length),
         format_(format),
         binary_(binary) { }
 
   void GetProgramBinary(GLuint program,
                         GLsizei buffer_size,
                         GLsizei* length,
                         GLenum* format,
                         GLvoid* binary) {
-    *length = length_;
+    if (length) {
+      *length = length_;
+    }
     *format = format_;
     memcpy(binary, binary_, length_);
   }
 
   void ProgramBinary(GLuint program,
                      GLenum format,
                      const GLvoid* binary,
                      GLsizei length) {
     // format and length are verified by matcher
     EXPECT_EQ(0, memcmp(binary_, binary, length));
@@ skipping 354 matching lines @@
   SetExpectationsForLoadLinkedProgram(kProgramId, &emulator);
 
   fragment_shader_->UpdateSource("different!");
   EXPECT_EQ(ProgramCache::PROGRAM_LOAD_SUCCESS, cache_->LoadLinkedProgram(
       kProgramId,
       vertex_shader_,
       fragment_shader_,
       NULL));
 }
 
+TEST_F(MemoryProgramCacheTest, OverwriteOnNewSave) {
+  const GLenum kFormat = 1;
+  const int kProgramId = 10;
+  const int kBinaryLength = 20;
+  char test_binary[kBinaryLength];
+  for (int i = 0; i < kBinaryLength; ++i) {
+    test_binary[i] = i;
+  }
+  ProgramBinaryEmulator emulator(kBinaryLength, kFormat, test_binary);
+
+  SetExpectationsForSaveLinkedProgram(kProgramId, &emulator);
+  cache_->SaveLinkedProgram(kProgramId, vertex_shader_, fragment_shader_, NULL);
+
+
+  char test_binary2[kBinaryLength];
+  for (int i = 0; i < kBinaryLength; ++i) {
+    test_binary2[i] = (i*2) % 250;
+  }
+  ProgramBinaryEmulator emulator2(kBinaryLength, kFormat, test_binary2);
+  SetExpectationsForSaveLinkedProgram(kProgramId, &emulator2);
+  cache_->SaveLinkedProgram(kProgramId, vertex_shader_, fragment_shader_, NULL);
+
+  SetExpectationsForLoadLinkedProgram(kProgramId, &emulator2);
+  EXPECT_EQ(ProgramCache::PROGRAM_LOAD_SUCCESS, cache_->LoadLinkedProgram(
+      kProgramId,
+      vertex_shader_,
+      fragment_shader_,
+      NULL));
+}
+
 }  // namespace gles2
 }  // namespace gpu