Disable building codec fuzzer when codec is disabled

Currently Chromium will build the related fuzzer for an image codec
when the codec has been disabled. This hasn't been an issue so far,
since the PDFium BUILD.gn is still building the codec code even when
it is disabled. It is just building it with a macro that disables the
logic.

This behaviour is going to soon change in PDFium, to having the codec
code not being built at all when it is disabled. This will break the
Chromium fuzzer builds. This CL turns off building the fuzzer when the
related fuzzer is disabled.

BUG=pdfium:1080

Change-Id: I6b1ff78c5b379fac9c29ca38b79c133c3d1367bb
Reviewed-on: https://chromium-review.googlesource.com/1050702Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557170}

pdf/pdfium/fuzzers/BUILD.gn

@@ -31,11 +31,7 @@ group("pdf_fuzzers") {
   if (pdf_enable_xfa) {
     deps += [
       ":pdf_cfx_barcode_fuzzer",
-      ":pdf_codec_bmp_fuzzer",
-      ":pdf_codec_gif_fuzzer",
       ":pdf_codec_jpeg_fuzzer",
-      ":pdf_codec_png_fuzzer",
-      ":pdf_codec_tiff_fuzzer",
       ":pdf_css_fuzzer",
       ":pdf_fm2js_fuzzer",
       ":pdf_formcalc_fuzzer",
@@ -43,6 +39,18 @@ group("pdf_fuzzers") {
       ":pdf_xml_fuzzer",
       ":pdfium_xfa_fuzzer",
     ]
+    if (pdf_enable_xfa_bmp) {
+      deps += [ ":pdf_codec_bmp_fuzzer" ]
+    }
+    if (pdf_enable_xfa_gif) {
+      deps += [ ":pdf_codec_gif_fuzzer" ]
+    }
+    if (pdf_enable_xfa_png) {
+      deps += [ ":pdf_codec_png_fuzzer" ]
+    }
+    if (pdf_enable_xfa_tiff) {
+      deps += [ ":pdf_codec_tiff_fuzzer" ]
+    }
   }
 }
 
@@ -146,21 +154,25 @@ fuzzer_test("pdf_streamparser_fuzzer") {
 }
 
 if (pdf_enable_xfa) {
-  fuzzer_test("pdf_codec_bmp_fuzzer") {
-    sources = []
-    deps = [
-      "//third_party/pdfium/testing/libfuzzer:pdf_codec_bmp_fuzzer",
-    ]
-    seed_corpus = "corpora/pdf_codec_bmp"
+  if (pdf_enable_xfa_bmp) {
+    fuzzer_test("pdf_codec_bmp_fuzzer") {
+      sources = []
+      deps = [
+        "//third_party/pdfium/testing/libfuzzer:pdf_codec_bmp_fuzzer",
+      ]
+      seed_corpus = "corpora/pdf_codec_bmp"
+    }
   }
 
-  fuzzer_test("pdf_codec_gif_fuzzer") {
-    sources = []
-    deps = [
-      "//third_party/pdfium/testing/libfuzzer:pdf_codec_gif_fuzzer",
-    ]
-    dict = "dicts/pdf_codec_gif.dict"
-    seed_corpus = "corpora/pdf_codec_gif"
+  if (pdf_enable_xfa_gif) {
+    fuzzer_test("pdf_codec_gif_fuzzer") {
+      sources = []
+      deps = [
+        "//third_party/pdfium/testing/libfuzzer:pdf_codec_gif_fuzzer",
+      ]
+      dict = "dicts/pdf_codec_gif.dict"
+      seed_corpus = "corpora/pdf_codec_gif"
+    }
   }
 
   fuzzer_test("pdf_codec_jpeg_fuzzer") {
@@ -172,27 +184,31 @@ if (pdf_enable_xfa) {
     seed_corpus = "corpora/pdf_codec_jpeg"
   }
 
-  fuzzer_test("pdf_codec_png_fuzzer") {
-    sources = []
-    deps = [
-      "//third_party/pdfium/testing/libfuzzer:pdf_codec_png_fuzzer",
-    ]
-    dict = "dicts/pdf_codec_png.dict"
-    seed_corpuses = [
-      "corpora/pdf_codec_png",
-      "//components/viz/test/data",
-      "//third_party/WebKit/LayoutTests/images/png-suite/samples",
-      "//third_party/WebKit/LayoutTests/images/resources/pngfuzz",
-    ]
+  if (pdf_enable_xfa_png) {
+    fuzzer_test("pdf_codec_png_fuzzer") {
+      sources = []
+      deps = [
+        "//third_party/pdfium/testing/libfuzzer:pdf_codec_png_fuzzer",
+      ]
+      dict = "dicts/pdf_codec_png.dict"
+      seed_corpuses = [
+        "corpora/pdf_codec_png",
+        "//components/viz/test/data",
+        "//third_party/WebKit/LayoutTests/images/png-suite/samples",
+        "//third_party/WebKit/LayoutTests/images/resources/pngfuzz",
+      ]
+    }
   }
 
-  fuzzer_test("pdf_codec_tiff_fuzzer") {
-    sources = []
-    deps = [
-      "//third_party/pdfium/testing/libfuzzer:pdf_codec_tiff_fuzzer",
-    ]
-    dict = "dicts/pdf_codec_tiff.dict"
-    seed_corpus = "corpora/pdf_codec_tiff"
+  if (pdf_enable_xfa_tiff) {
+    fuzzer_test("pdf_codec_tiff_fuzzer") {
+      sources = []
+      deps = [
+        "//third_party/pdfium/testing/libfuzzer:pdf_codec_tiff_fuzzer",
+      ]
+      dict = "dicts/pdf_codec_tiff.dict"
+      seed_corpus = "corpora/pdf_codec_tiff"
+    }
   }
 
   fuzzer_test("pdf_css_fuzzer") {