Scale down a slow index buffer perf test.

This test was slow enough that running 20k iterations might have been
causing a timeout on the Nexus 5.

Bug: angleproject:2923 
Change-Id: I03f6e95135d8c521e6ef3e81bc9a4b0dfd7f19df
Reviewed-on: https://chromium-review.googlesource.com/c/1310693
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

src/tests/perf_tests/DrawElementsPerf.cpp

@@ -199,6 +199,11 @@ DrawElementsPerfParams DrawElementsPerfD3D11Params(bool indexBufferChanged,
         useNullDevice ? angle::egl_platform::D3D11_NULL() : angle::egl_platform::D3D11();
     params.indexBufferChanged = indexBufferChanged;
     params.type               = indexType;
+
+    // Scale down iterations for slower tests.
+    if (indexBufferChanged)
+        params.iterationsPerStep /= 100;
+
     return params;
 }
 
@@ -207,6 +212,11 @@ DrawElementsPerfParams DrawElementsPerfD3D9Params(bool indexBufferChanged)
     DrawElementsPerfParams params;
     params.eglParameters      = angle::egl_platform::D3D9();
     params.indexBufferChanged = indexBufferChanged;
+
+    // Scale down iterations for slower tests.
+    if (indexBufferChanged)
+        params.iterationsPerStep /= 100;
+
     return params;
 }
 
@@ -216,6 +226,11 @@ DrawElementsPerfParams DrawElementsPerfOpenGLOrGLESParams(bool indexBufferChange
     params.eglParameters      = angle::egl_platform::OPENGL_OR_GLES(false);
     params.indexBufferChanged = indexBufferChanged;
     params.type               = indexType;
+
+    // Scale down iterations for slower tests.
+    if (indexBufferChanged)
+        params.iterationsPerStep /= 100;
+
     return params;
 }
 
@@ -228,6 +243,11 @@ DrawElementsPerfParams DrawElementsPerfVulkanParams(bool indexBufferChanged,
         useNullDevice ? angle::egl_platform::VULKAN_NULL() : angle::egl_platform::VULKAN();
     params.indexBufferChanged = indexBufferChanged;
     params.type               = indexType;
+
+    // Scale down iterations for slower tests.
+    if (indexBufferChanged)
+        params.iterationsPerStep /= 100;
+
     return params;
 }