Make reload button clear the network cache.

[jdm]

The developer workflow in FxR is frustrating right now because of bugs like #24385. To allow us to put out a new release soon that addresses this papercut, these changes make the reload button clear the network cache in FxR.

---

• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix (kind of) #26411.
• These changes do not require tests because can't test FxR.

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/constellation/constellation.rs
• @cbrewster: components/constellation/constellation.rs
• @KiChjang: components/net/resource_thread.rs, components/net_traits/lib.rs, components/net/http_cache.rs

[highfive]

Warning

• These commits modify net code, but no tests are modified. Please consider adding a test!

[jdm]

r? @Manishearth

[Manishearth]

@bors-servo r+

Would be nice to clear the current page's cache only (basically, the equivalent of shift-reload on Firefox), but that's fine.

[bors-servo]

📌 Commit 8f4f5cf has been approved by Manishearth

[bors-servo]

⌛ Testing commit 8f4f5cf with merge 958aaa1...

[bors-servo]

💔 Test failed - status-taskcluster

[jdm]

@bors-servo r=Manishearth

[bors-servo]

📌 Commit 9b1307e has been approved by Manishearth

[bors-servo]

⌛ Testing commit 9b1307e with merge db700b5...

[bors-servo]

💔 Test failed - status-taskcluster

[jdm]

@bors-servo r=Manishearth

[bors-servo]

📌 Commit f030162 has been approved by Manishearth

[bors-servo]

⌛ Testing commit f030162 with merge 6cddce7...

[bors-servo]

💔 Test failed - status-taskcluster

[jdm]

@bors-servo retry

• #25522

[bors-servo]

⌛ Testing commit f030162 with merge 223fb00...

[bors-servo]

💔 Test failed - status-taskcluster

[Manishearth]

@bors-servo retry

• network error running filter-intermittents

[bors-servo]

⌛ Testing commit f030162 with merge 746ece7...

[bors-servo]

💔 Test failed - status-taskcluster

[Manishearth]

@bors-servo retry

• font cache crash #21067

  │ error: XDG_RUNTIME_DIR not set in the environment.
  │ libEGL warning: No hardware driver found, falling back to software rendering
  │ Failed to receive a response from live font cache (thread LayoutThread PipelineId { namespace_id: PipelineNamespaceId(1), index: PipelineIndex(1) }, at components/gfx/font_cache_thread.rs:513)
  │    0: servo::backtrace::print
  │    1: servo::main::{{closure}}
  │    2: std::panicking::rust_panic_with_hook
  │              at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libstd/panicking.rs:530
  │    3: std::panicking::begin_panic
  │    4: <gfx::font_cache_thread::FontCacheThread as gfx::font_context::FontSource>::get_font_instance
  │    5: gfx::font_context::FontContext<S>::font
  │    6: gfx::font::FontGroup::first
  │    7: layout::text::font_metrics_for_style
  │    8: layout::inline::InlineFlow::minimum_line_metrics_for_fragments
  │    9: std::thread::local::LocalKey<T>::with
  │   10: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block_starting_with_fragments
  │   11: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block_like
  │   12: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block
  │   13: <layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode> as layout::traversal::PostorderNodeMutTraversal<ConcreteThreadSafeLayoutNode>>::process
  │   14: layout::traversal::construct_flows_at
  │   15: style::traversal::DomTraversal::handle_postorder_traversal
  │   16: profile_traits::time::profile
  │   17: layout_thread::LayoutThread::handle_reflow
  │   18: profile_traits::time::profile
  │   19: layout_thread::LayoutThread::handle_request_helper
  │   20: layout_thread::LayoutThread::start
  │   21: profile_traits::mem::ProfilerChan::run_with_memory_reporting
  │   22: std::sys_common::backtrace::__rust_begin_short_backtrace
  │   23: core::ops::function::FnOnce::call_once{{vtable.shim}}
  │   24: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
  │              at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/liballoc/boxed.rs:1074
  │       <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
  │              at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/liballoc/boxed.rs:1074
  │       std::sys::unix::thread::Thread::new::thread_start
  │              at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libstd/sys/unix/thread.rs:87
  │   25: start_thread
  │   26: __clone
  │ [2020-07-28T06:39:54Z ERROR servo] Failed to receive a response from live font cache
  │ Pipeline failed in hard-fail mode.  Crashing!
  │ thread panicked while processing panic. aborting.
  └ thread panicked while processing panic. aborting.

[bors-servo]

⌛ Testing commit f030162 with merge 0ce3ad5...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: Manishearth
Pushing 0ce3ad5 to master...