Print error from driver when shader compiler fails

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2248853002

Review-Url: https://codereview.chromium.org/2248853002
diff --git a/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp b/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
index 296c2be..d2e49a5 100644
--- a/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
@@ -73,6 +73,7 @@
                 GrGLsizei length = GR_GL_INIT_ZERO;
                 GR_GL_CALL(gli, GetShaderInfoLog(shaderId, infoLen+1, &length, (char*)log.get()));
                 print_shader_source(strings, lengths, count);
+                SkDebugf("\n%s", (const char*)log.get());
             }
             SkDEBUGFAIL("Shader compilation failed!");
             GR_GL_CALL(gli, DeleteShader(shaderId));