disable linear pipeline for now (so bots don't crash)

src/core/SkBitmapProcShader.cpp

Index: src/core/SkBitmapProcShader.cpp
diff --git a/src/core/SkBitmapProcShader.cpp b/src/core/SkBitmapProcShader.cpp
index 59b3f57700783128f9940dc4f7e08fcba18db8f6..f26194280c579cfe4a34f2c16f1564e171359562 100644
--- a/src/core/SkBitmapProcShader.cpp
+++ b/src/core/SkBitmapProcShader.cpp
@@ -226,6 +226,11 @@ SkShader::Context* SkBitmapProcShader::MakeContext(const SkShader& shader,
         useLinearPipeline = false;
     }
 
+    //
+    // For now, only enable locally since we are hitting some crashers on the test bots
+    //
+    useLinearPipeline = false;
+
     if (useLinearPipeline) {
         void* infoStorage = (char*)storage + sizeof(LinearPipelineContext);
         SkBitmapProcInfo* info = new (infoStorage) SkBitmapProcInfo(provider, tmx, tmy);