Performance experiment: Disable SkSL inliner in nanobench/skpbench.

This is a reland of 3f35ac10b4

Time to run this experiment again.

Original change's description:
> Performance experiment: Disable SkSL inliner in nanobench/skpbench.
>
> This will allow us to measure the impact (positive or negative) of
> inlining functions before submitting a shader to the driver.
>
> Change-Id: Icbd64096445a353187b30feea68573d89ca18664
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/384317
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>

Change-Id: I278a770d4129f4ad0bf867c33a01b49a88cea588
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/387256
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>

bench/nanobench.cpp

@@ -80,6 +80,10 @@ extern bool gSkVMJITViaDylib;
 #include "src/gpu/gl/GrGLUtil.h"
 #include "tools/gpu/GrContextFactory.h"
 
+namespace SkSL {
+extern bool gSkSLInliner;
+}
+
 using sk_gpu_test::ContextInfo;
 using sk_gpu_test::GrContextFactory;
 using sk_gpu_test::TestContext;
@@ -1241,6 +1245,7 @@ int main(int argc, char** argv) {
     gSkForceRasterPipelineBlitter = FLAGS_forceRasterPipeline;
     gUseSkVMBlitter = FLAGS_skvm;
     gSkVMAllowJIT = gSkVMJITViaDylib = FLAGS_jit;
+    SkSL::gSkSLInliner = false;  // Temporary experiment
 
     int runs = 0;
     BenchmarkStream benchStream;

tools/skpbench/skpbench.cpp

@@ -88,6 +88,10 @@ static const char resultFormat[] =
 
 static constexpr int kNumFlushesToPrimeCache = 3;
 
+namespace SkSL {
+extern bool gSkSLInliner;
+}
+
 struct Sample {
     using duration = std::chrono::nanoseconds;
 
@@ -497,6 +501,8 @@ int main(int argc, char** argv) {
         exit(0); // This can be used to print the header and quit.
     }
 
+    SkSL::gSkSLInliner = false;  // Temporary experiment
+
     // Parse the config.
     const SkCommandLineConfigGpu* config = nullptr; // Initialize for spurious warning.
     SkCommandLineConfigArray configs;