Check that the shader source exists before loading from the ProgramCache.

gpu/command_buffer/service/program_manager.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/program_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1264 matching lines @@
   ClearLinkStatus();
 
   if (!AttachedShadersExist()) {
     set_log_info("missing shaders");
     return false;
   }
 
   TimeTicks before_time = TimeTicks::Now();
   bool link = true;
   ProgramCache* cache = manager_->program_cache_;
-  if (cache) {
-    DCHECK(!attached_shaders_[0]->last_compiled_source().empty() &&
-           !attached_shaders_[1]->last_compiled_source().empty());
+  if (cache &&
+      !attached_shaders_[0]->last_compiled_source().empty() &&
+      !attached_shaders_[1]->last_compiled_source().empty()) {
     ProgramCache::LinkedProgramStatus status = cache->GetLinkedProgramStatus(
         attached_shaders_[0]->last_compiled_signature(),
         attached_shaders_[1]->last_compiled_signature(),
         &bind_attrib_location_map_,
         transform_feedback_varyings_,
         transform_feedback_buffer_mode_);
 
     bool cache_hit = status == ProgramCache::LINK_SUCCEEDED;
     UMA_HISTOGRAM_BOOLEAN("GPU.ProgramCache.CacheHit", cache_hit);
 
@@ skipping 1362 matching lines @@
   DCHECK(program);
   program->ClearUniforms(&zero_);
 }
 
 int32_t ProgramManager::MakeFakeLocation(int32_t index, int32_t element) {
   return index + element * 0x10000;
 }
 
 }  // namespace gles2
 }  // namespace gpu