Fix vulkan build on linux and android

src/gpu/vk/GrVkPipelineStateCache.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrVkResourceProvider.h"
 
 #include "GrVkGpu.h"
@@ skipping 86 matching lines @@
 #ifdef GR_PIPELINE_STATE_CACHE_STATS
     ++fTotalRequests;
 #endif
     // Get GrVkProgramDesc
     GrVkPipelineState::Desc desc;
     if (!GrVkProgramDescBuilder::Build(&desc.fProgramDesc,
                                        primProc,
                                        pipeline,
                                        *fGpu->vkCaps().glslCaps())) {
         GrCapsDebugf(fGpu->caps(), "Failed to build vk program descriptor!\n");
-        return false;
+        return nullptr;
     }
 
     // Get vulkan specific descriptor key
     GrVkPipelineState::BuildStateKey(pipeline, primitiveType, &desc.fStateKey);
     // Get checksum of entire PipelineDesc
     int keyLength = desc.fStateKey.count();
     SkASSERT(0 == (keyLength % 4));
     // Seed the checksum with the checksum of the programDesc then add the vulkan key to it.
     desc.fChecksum = SkChecksum::Murmur3(desc.fStateKey.begin(), keyLength,
                                          desc.fProgramDesc.getChecksum());
@@ skipping 30 matching lines @@
         entry->fPipelineState = std::move(pipelineState);
         fHashTable.set(entry);
         fLRUList.addToTail(entry);
         return entry->fPipelineState;
     } else {
         fLRUList.remove(entry);
         fLRUList.addToTail(entry);
     }
     return entry->fPipelineState;
 }